In　the　drive　system　of　permanent　magnet　synchronous　motor(PMSM)　controlled　by　inner-loop　field　orientation　control(FOC)　and　outer-loop　classical　proportional　integral(PI),　it　is　prone　to　appear　uncertain　defects　such　as　low　detection　accuracy　of　external　disturbance,　chattering　and　large　overshoot　of　speed　loop.　In　order　to　solve　the　chattering　problem　of　PI　control　and　improve　the　anti-interference　ability　of　the　system,　an　integral　super　twisting　sliding　mode　controller(ISTSMC)　is　proposed.　In　order　to　realize　sensorless　control　and　online　estimation　of　motor　speed　and　position,　the　sliding　mode　observer　based　on　extended　Kalman　filter(EKF)　is　also　designed,　and　a　piecewise　sinusoidal　function　is　designed　to　replace　the　traditional　sgn　function　based　sliding　mode　observer　to　reduce　chattering.　In　Matlab/Simulink　simulation,　the　speed　response　and　detection　accuracy　of　the　system　under　various　fault　disturbances,　reverse　operation　and　load　disturbances　are　analyzed.　The　results　prove　the　feasibility　and　superior　dynamic　performance　of　the　proposed　system.　©　2024　Editorial　Office　of　Journal　of　Electrical　Engineering.　All　rights　reserved.