Abstract: The constitution,working principle and size design method of double sides LSRM were introduced and size design result of a LSRM prototype was given.Distribution rule of LSRM's magnetic field was analyzed by use of finite element method and sectioned magnetic field was consulted,so as to get the maximum induction value,the minimum induction value and the number of windings. The testing result showed that the starting power of the LSRM prototype is large and it would not affected by direction of current.But there are some problems of pulse and noise in starting,which could be solved by use of optimization of structure design and control algorithm.