Abstract: Through analyzing structural property and magnetic property of the primary pump bolts in the third generation nuclear power plant EPR pressurized water reactor and based on the fact that the primary pump bolts are liable to produce transverse crack in service, it is proposed that the primary pump bolts of threaded area are inspected by using segmental magnetization and coil residual magnetic method. The results show that the above-mentioned method is superior to the continuous magnetizing method used in foreign nuclear power station.