The Han dynasty ruled the whole of China for more than 400 years from 202 B.C. to 220 A.D. There was a short period of fifteen years from 9-23 A.D., when Wang Mang usurped the throne and called his new dynasty Xin, which meant new. His vision was to revive the virtues of the sage kings of the Zhou, but he lasted only a short time, and the civil war that followed resulted in the restoration of the Han. The first part of the Han is known as the Western Han and the last part as the Eastern Han.
The fall of the Qin was caused by too much bureaucracy and control, but it did not cause a complete return to the feudal society of the Zhou period. 14 of the Qin commanderies were kept in the western part of the empire, but the princes of the emperor's family ruled the eastern half in 10 kingdoms (Fairbank p. 57). 
The cost of large-scale military operations against the Xiongnus, a federation of nomadic Turkish tribes, was a heavy burden on the people. Monopolies on salt and iron, among other things, were instated, and the annual taxes were paid in copper coins (Wills p. 73). 

Initially, minting was allowed to be done by merchants or local authorities, but this also became a state monopoly in 112 B.C. (Yang p. 16). In the first century about 220,000 strings of 1000 coins were minted on average per year. This had to supply the needs of a population of 60 million, and according to Fairbank (p. 60) this was not a sign of a highly developed money economy (3,7 coin per inhabitant per year). 

The casting of coins during the Western Han was done with a more sophisticated technique, that made the coins more uniform. Before this period most coin moulds had had to be broken to release the coins. When using the new system, the moulds were also broken, but the clay mould was made with a so-called mother- bronze mould, and therefore it was very easy to standardize the moulds, and this way it was possible to use skilled craftsmen and artists to incise the mould as the work only had to be done once. Especially the coins of Wang Mang are works of fine art (Peng p. 117). See casting techniques.

During the Han the Ban Liang and the Wu Zhu were the most important coins. Money cast in silver/tin alloy, tortoise shells and deer hide notes were also issued, but Peng says that these types of money had special functions, and were not circulated (Peng p. 106).

Western Han.
Gold ingots were still used in the Western Han for large money transactions, and one Jin was, in emperor Wu’s time, probably equal to 10.000 Ban Liang (Peng p. 102). The weight of the Ban Liang was in 186 B.C. reduced from the original 12 zhu to 8 zhu, and in 175, it was again reduced to 4 zhu. 

There were three main types of bronze coins cast during the Western Han: The Ban Liang, The San Zhu (3 zhu) and the Wu Zhu (5 zhu), but they were cast in many variations of weight and style.

The Ban Liang were cast in three values, the 12, 8 and 4 zhu. Early Ban Liangs had no rims, some later types had rims. 

The Wu Zhu replaced the Ban Liang, and the first Wu Zhu was cast by emperor Wu in 118 B.C. The Wu Zhu of the Han had a stable size and weight which corresponded to the actual weight of the zhu unit, and it had raised rims on both sides that protected the inscription. It is the coin type that has been used for the longest period in Chinese history. Even the coin types issued after the Tang imitated its weight and size (Peng p. 107). The type of Wu Zhu called the red-edged Wu Zhu is, according to Peng (p. 106), a misunderstanding, and should not be considered a specific type of Wu Zhu: it was only due to the fact that Wu Zhu’s began to have their edges filed.

Wang Mang.
Probably because the Zhou period was a golden era in the eyes of Wang Mang, he reinstated the knife and spade coins as well as gold, silver and shells alongside the round bronze coins. According to Yang (p. 16), there were 28 denominations in five materials. This was too confusing and was abolished already in 14 A.D. After this the Huo Quan became the standard currency together with different types of spade coins. The Huo Quan weighed 5 zhu and the spade coins were equal to 5 Huo Quan.

Eastern Han.
After the coins of Wang Mang's interregnum were abolished by the Eastern Han, the Wu Zhu began to be minted again as the only currency of the period.