Objective:To investigate radionuclide deposition in the systems related to the primary loop during the overhaul and refueling at a nuclear power plant.Methods:The radionuclides deposited in the main piping system, the primary loop coolant purification system, the volume and boron control system, the waste heat export system, and the inner wall of pipe in boron-containing water system were measured by using the low and medium radiation field high-purity germanium (HPGe) in-situ γ source term measurement system, the strong radiation field cadmium zinc telluride (CZT) in- situ γ source term measurement system, and the portable radiation monitoring instrument Radiagem-2000. Results:The result had shown that the major radionuclides deposited in the systems related to primary loop were mainly 58Co, 60Co, 95Nb, 95Zr, 51Cr, 124Sb, 54Mn, 110Ag *, 59Fe, and those with higher deposition were 60Co, 58Co, 124Sb, 95Zr. Of them, the largest deposition was 60Co up to 21 200 Bq/cm 2 in extra strong pipe below the safety valve, 58Co up to 8 480 Bq/cm 2 in the pipeline of hot section in the state of full water in the main pipeline. 124Sb was 4 910 Bq/cm 2 in pipeline before the filter of the primary loop purification system and 4 680 Bq/cm 2 in the chemical capacity drainage pipeline, respectively, and 95 Zr was 2 500 Bq/cm 2 in the pipeline of hot section in the state of full water in the main pipeline. The radionuclides deposited, after the filter of the purification system, in the pipe upstream of the boron-containing pump were significantly lower than those in other systems. Conclusions:The types of radionuclides in the systems associated with primary loop at a nuclear power plant are basically identical, but their amount deposited varies greatly. Attention should be paid to the removal of radionuclides in primary loop through the filter of purification system.