Abstract: The calculation accuracy for a temperature rise of winding and primary water in the canned motor of nuclear main pump is crucial to the motor life and bearing safety in operation. In the current work, the spiral tube heat exchanger is arranged outside the casing between the upper and lower end cavity of the stator winding in nuclear main pump canned motor for small reactors. Based on the computational fluid dynamics (computational fluid dynamics, CFD) method, the three-dimensional RANS two-equation SST k-ω turbulence model and other conservation equations under thermal rated conditions are solved. The sensitivity of the temperature for solid parts such as stator winding insulation peak value, shell, etc., and for cooling water in clearance between stator and rotor, in lower guide bearing to the thermal conductivities of equivalent insulation, the axial thermal conductivity of core laminations which have uncertainty and the variation of secondary water inlet temperature are studied. By comparing with experimental data and research experience, the values of equivalent insulation thermal conductivity and axial thermal conductivity of core can be obtained. The results show that except for the peak temperature of stator winding insulation, other solid-liquid temperatures are not sensitive to the change of equivalent insulation thermal conductivity and axial thermal conductivity of stator and rotor core lamination, but sensitive to the evolution of secondary cooling water inlet temperature. It provides a reference for the water cooling design of similar motors.