The protection of painting layer of Qin Terracotta Army is the key and difficult problem in the protection of Qin Shihuang Mausoleum. Based on the comprehensive introduction of the present state of Qin Terracotta Army, its cause of being destroyed were analyzed. The factors such as history, mechanics, physics and chemistry mutually caused the destruction. Two protecting methods, one was combining PEG200 and PU latex, the other was monomer infiltrated solidified by electron beam, were particular evaluated. The advantage and disadvantage of the two methods were analysed the principium and operation of some assistant reinforce technologies such as frozen drying method, salt aqua drying method and room temperature drying method were introduced. Then some conceived method that producing reinforce materials incorporated with protecting terracotta figures, uniform field and steadying lacquer layer were put forward.