Different physical simulation welding parameters were performed using Gleeble-3500 type thermal simulator to research the effect of thermal cycle on microstructure transition and property variation of boron steel 22MnB5. The peak temperature of welding thermal cycle was set to 1320-870°C, and cooling rates t8/5 to 6s-100s. Then microstructure observation, hardness detection, and impact toughness tests were carried out to clarify the effect of different thermal cycles. The results show that 22MnB5 has good mechanical properties, but the toughness decreases obviously under certain thermal cycles, showing cold crack sensitivity of 22MnB5. Martensite and ferrite are the main microstructure under different peak temperature and t8/5.