On the basis of negative sequence current generation mechanism analysis of synchronous generatorstator winding inter-turns short circuit，the method of detecting and diagnosing synchronous generator stator windinginter-turns short circuit is proposed，which uses the negative sequence current as fault signature. A field-circuitcoupled mathematical model of synchronous generator is built，based on the field-circuit coupled principle. Firstly，stator winding inter-turns short circuit happened in synchronous generator with half load is simulated. And thenthree-phase current phase difference，amplitude and negative sequence current component before and after fault iscalculated according to the model. The accuracy of model and rationality of theoretical analysis is demonstrated bythe use of experimental data coming from 24 kW synchronous. Meanwhile，the short circuit fault with the samebranch and different branch impact on the negative sequence current is also simulated and analyzed. The resultshave some significance for synchronous generator stator winding inter-turns circuit fault monitoring and diagnosis.