Abstract: With the welding heat-cycle system which voluntarily design, through measuring temperature signal in real-time tests on different positions of two welded joints under the different welding parameters.The effects of peak temperature of welding thermal circle on hardness of 10CrMo910 have been researched.The test result indicated that welding heat-cycle has a greater influence on the value of hardness, when the peak value temperature is lower than 1 150℃, hardness value increases with the peak value temperature increasing;when the peak value temperature is higher than 1 150℃, hardness value decreases with the peak value temperature increasing.