Abstract: The influence of welding parameters(pressure and current) on the size of nugget and heat-affect zone is obtained by analysing the microstructure of the nugget of the high-strength aluminum spot welding,the correlation between the parameters and the microstructure is obtained too,and the detailed influence of the little variation of the welding parameters and the less distinct change of the signals on welding nugget quality is observed,which lay a foundation for the further study of precise control of the spot welding process.The building model and the simulation of spot welding are achieved through finite element analysis software SYSWELD,and the relationship between the electrode pressure,welding current and nugget size is studied respectively.