Abstract: Taken a 400 W off-grid type permanent magnet synchronous generator as an example,the 2-D model of electromagnetic field was established.By using the field-circuit coupled method,the electromagnetic parameters of prototype with different loads and speeds were calculated.Based on the original structure design of prototype,two kinds of rotor structures were proposed and compared in terms of the no-load leakage coefficient,anti-EMF waveforms and the harmonic content of air-gap flux density;and the influences of these two structures on the electromagnetic performance of generators were analyzed.According to the heat transferring theories,the heat losses evaluated by the electromagnetic analysis were taken as the distributed heat sources;and the 2-D calculation model of temperature field for the whole area was built.The relationship between wind speed ,load and temperature distribution,through calculation and analysis of temperature field under different wind speed and load conditions,can be gained.Electromagnetic and thermal performance tests were studied;and it was showed that the test values were almost equal to the calculated ones,so some useful conclusions can be drawn to provide support for design and optimization of the off-grid type permanent magnet synchronous generator.