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.