More than one hundred bronze molds for casting bronze coins of Han dynasty (206B.C.-A.D. 220) have been found in Shaanxi, Henan, Shandong, Jiangsu and Anhui provinces in China. The most important are the 41 pieces bronze molds for casting Wu Zhu coins unearthed from a kiln in Chencheng, Shaanxi province in 1979. The archaeologists dated them to the Western Han Dynasty between 118 B.C. and 113 B.C. A few bronze molds for casting coins before Qin Dynasty and after Han Dynasty were found in China. Bronze mold casting for bronze coins was an important casting technology in Han Dynasty. The development and properties of bronze molds were studied in this paper. These bronze molds of Han dynasty show that the main style is that with one sprue gate and symmetrically distributing cavities on the both sides of the sprue gate one by one. The bronze - mold size gradually increased from the early Western Han until to the later Western Han and Xin Empire, then decreased. Most of bronze - molds had the two rows coin - cavities in the early Western Han, two and four rows of coin - cavities in the middle Western Han, then four and six rows coin - cavities in the late Western Han and Xin Dynasty. The bronze molds casting for coin came down in the Eastern Han, when most molds had only two rows coin of cavities on the both sprue gate's sides. The compositions of 21 bronze - molds were analyzed by XRF, their surfaces corrosion was not cleaned because they are the valuable collection of Shanghai Museum. Consequently, the composition is qualitative, not quantitative. In the copper, tin and lead content distribution diagram, the spots of tin and lead contents scattered in the early Western Han; the 14 molds had a lower tin content and higher lead content, more than 70 percent of lead content are up 20% from the middle Western Han to the Eastern Han; the spots of tin and lead contents concentrated on a small area in the Xin. So most bronze molds had a lower tin content and a higher lead content in the Han Dynasty. Four samples were removed from the bronze - molds, one from early Western Han, two from late Western Han and one from Eastern Han. Polishing, not etching, the microstructure of samples shows the dendrite structure with [alpha] phase and lead, or [alpha] phase, ([alpha] + [delta]) eutectoid and lead under a metallurgical microscope. This kind of structure made the bronze mold with the higher plasticity and density. The molds still kept a dendrite structure after casting bronze coins by hundreds times. It proved these bronze molds kept from a high temperature for a long time. So a coating should be used on the cavity's surface to protect the bronze mold.