Abstract: When 10MW high temperature gas cooling reactor restarts in short time after hot shutdown, the reactor could start and rise the power quickly and save much time. However, the temperature of steam generator keeps high （about 430℃） after hot shutdown , and the temperature of the secondary loop is about 100℃. The large temperature differences will generate high thermal stress and thus lead fatigue damage at the weld joint of the tube and tube-plate of steam generator. This paper will analyzis the temperature differences, calculate the stress level and evaluate the fatigue damage of weld joint of steam generator in HTR-10.