In　this　paper,　an　improved　sliding　mode　observer　with　an　improved　sliding　mode　load　torque　observer　is　proposed　for　permanent　magnet　synchronous　motor　drive　systems.　The　sliding　mode　load　torque　observer　can　quickly　estimate　the　load　torque　and　perform　feedforward　compensation　to　reduce　the　impact　of　load　disturbance　on　the　speed.　In　order　to　improve　the　tracking　accuracy　of　the　traditional　sliding　mode　observer　and　reduce　system　chattering,　a　variable　boundary　layer　saturation　function　is　used　to　replace　the　sign　function.　Simulation　and　corresponding　results　demonstrate　that　the　system　has　high　tracking　accuracy　and　small　errors　in　position　and　speed　estimation,　and　has　strong　robustness　against　load　torque　disturbances.　©　2020　IEEE.