Abstract: The Article 192 of Chinese Criminal Procedural Code provides that,the prosecutor,litigants and the counsels have the right to apply for the writ of the court summoning the expert assistant to attend the court and make a judgment about the expert opinion,which guarantees the accuracy of forensic science and clear the hindrance to the Trial Centralism Policy. However,without the rules of the implementation,because of the omission of duty,status,right and responsibility of the expert assistant,the aim of the law can hardly be realized. Throughout the world,the expert assistant system is not the initiative of China,in Russia and Italy the related regulations are extremely sophisticated and the introduction of which into China can help us to perfect the system and to implement the Trial Centralism Policy.