Abstract: In view of the problem of anti-carburizing in the production process of internal thread,this paper studied the process of anti-carburizing isolation about the internal thread of plugging by T3 copper and 20 steel bolts by means of simulation and carburizing and quenching. The sealing of internal thread and external thread after expansion at high temperature was simulated, and the anti-carburizing isolated effect of internal thread after carburizing and quenching were verified by experiment. The results show that,the passage that the carburizing atmosphere enter the hole is smaller than that of 20 steel when the T3 copper plug is used. Under the condition of 930℃×21h carburizing,the hardness of each screw tooth of internal thread separated by T3 copper plug is lower than that of 20 steel,and the hardness fluctuation is smaller than that of 20 steel. the former has the characteristics of high protection, high stability and high economy.