A high power direct drive variable-speed constant-frequency wind energy conversion system based on multi-phase permanent magnet synchronous generator (PMSG) is researched. In order to reduce the current of each winding and each power electronics converter, six-phase PMSG and multiple AC-DC-AC converters are used. A sensorless control strategy of six-phase PMSG based on model reference adaptive system (MRAS) is researched. In this strategy, the PMSG is regarded as reference model while the current model of PMSG is considered as adjustable model. The adaptive laws are designed so that generator speed and rotor position are estimated at the same time. Maximum power point tracking (MPPT) control strategy based on step-changing climbing method is also researched. This method has a fast dynamic response and a good steady state. Experimental results prove that the proposed method is capable of precisely estimating the generator speed and rotor position under the condition of load change and speed change. When the wind speed is changing, the proposed method can also track the maximum power point.