Abstract: Through resistance spot welding technology test, formation process of 6016-T4P plate lap welding spot nugget with three thicknesses of 2.5 mm, 3.2 mm and 2.0 mm was analyzed. And two different shape electrode caps (ϕ16R20, ϕ20R100) commonly used in main engine factory were used for technology test respectively, and the corresponding resistance spot welding process window was established. Meanwhile, influence of electrode pressure and electrode cap shape on the shift of welding process window was analyzed. The results showed that when ϕ16R20 electrode cap was used, change of electrode pressure (3.5～5.5 kN) could make the minimum welding current available to welding spot change by 1 kA. When ϕ20R100 electrode cap was used, change of electrode pressure (3.5～5.5 kN) could make the minimum welding current change of 3 kA. Under the same welding parameters (electrode pressure 4.5 kN, welding time 200 ms, holding time 150 ms), change of electrode cap shape (ϕ16R20 electrode cap, ϕ20R100 electrode cap) could make the minimum welding current available to welding spot change by 5 kA. The research results of this paper could significantly improve the situation that resistance spot welding process window did not match in the promotion and application of aluminum alloy in the aluminum alloy production plant, facilitate the material switching, and be conducive to the promotion and application of aluminum alloy in the main engine plant.