Abstract: For the study of steam generator（SG） heat exchange tube flow distribution and its effect on the reactor coolant pump（RCP） entrance flow, the scale model experiment in the cold state of the SG was conducted. The experimental data was the new inflow condition of the SG channel head. The three-dimensional flow field of the SG channel head was calculated by CFD method. The results show that the SG heat exchange tubes have serious uneven flow distribution. The SG entrance will have a greater impact on the flow distribution of the heat exchange tube, especially the tubes toward the entrance. The partial flow rate increases and the formation of high speed creates a relatively low velocity zone and the recirculation zone around itself; when the flow rate is small, the distance head of the heat exchange tube plays a leading role; the uneven flow distribution in the heat exchanger tubes of the SG will cause the axial velocity at the outlet of the SG to be even more turbulent.