In　this　paper,　a　nonlinear　control　method　based　on　fractional-order　sliding　surface　is　developed　for　position　tracking　control　of　permanent　magnet　synchronous　motor　(PMSM).　First,　a　fractional-order　sliding　mode　controller　(FOSMC)　is　designed　to　achieve　desirable　transient　dynamics　while　avoiding　the　strong　chattering　effect　of　classical　sliding　modes.　Next,　a　super-twisting　disturbance　observer　(STDOB)　is　introduced　to　estimate　and　compensate　for　the　adverse　effects　of　lumped　unknown　disturbances　in　PMSM.　Lyapunov　functions　are　used　to　analyze　stability　of　the　proposed　control　strategy.　Finally,　the　performance　and　robustness　of　the　proposed　composite　control　scheme　are　demonstrated　by　experimental　results.　©　2023　Technical　Committee　on　Control　Theory,　Chinese　Association　of　Automation.