Abstract: The software for welding heat simulating was developed successfully based on some classical mathematic models, measured data and programmed appropriately by LabVIEW8.2 and STEP7.The interface is simple to draw welding heat simulating curve with this software.Setting parameters of interval time for multipass welding heat simulating experiments can make the preheat temperature be consistent to the setting value.The software with good stability, reliability and conveniency has been applied to the series of domestic thermo-mechanical simulator, which consummates the simulator's functions.