Qinglong Town was built in 746 AD and was the earliest foreign trade center in Shanghai. An archaeological excavation at Qinglong Town in 2012 discovered four furnaces, a large number of casting moulds and slag, etc. It was a foundry site and was used for a long time in the Tang Dynasty. From the cross section of a casting mould, there are three layers:cavity surface layer, interlayer and outer layer. Three layers have different effects. The cavity surface layer ensures a smooth casting surface. The interlayer increases the intensity of moulds and reduces the mould shrinkage and deformation in drying. The outer layer includes a lot of rice husk made for the venting of the mould cavity. The moulds indicate that the foundry workers in Qinglong Town used professional mould making technology. The foundry workers could successfully cast ironware.