The　ultra-high　strength　quenched　22MnB5　steel　is　researched　in　this　paper,　the　intermediate　frequency　inverter　&　electric　servo　welding　gun　system　is　used　to　weld　the　sheets,　experiments　included　of　tensile-shear　with　synchronous　electrical　testing,　microstructure　of　the　material　and　fractures　analysis　and　the　Vickers-Hardness　testing.　The　results　point　out　that　the　maximum　hardness　is　located　at　weld　nugget,　and　the　minimum　hardness　is　appeared　in　heat　affected　zone　(HAZ).　Fracture　is　formed　under　the　combined　effects　of　shear　stress　and　normal　stress,　the　shear　stress　contributes　to　interfacial　fracture,　and　leads　to　rupture.　Non-uniformity　of　the　microstructure　caused　by　spot　welding,　changed　the　property　of　the　material　in　nugget,　stress-strain　relationship　of　this　area　is　nonlinear.　The　results　also　show　that　the　conventional　weld　size　guidance　of　4　root　t　is　not　sufficient　to　produce　nugget　pullout　failure　mode　for　22MnB5　UHSS　spot　welds.