The primary current of the multiphase linear induction motor(LIM) reaches tens of thousands of amperes in short-time pulse operation. The motor end windings are subject to a large amount of alternating electromagnetic force. Accurate calculation of the alternating electromagnetic force is the theoretical basis for the fixed design of the end windings. Taking the end structure of twelve-phase LIM as the research object, based on Biot-Savart law, this paper calculates the magnetic density and electromagnetic force density in different directions of each end winding segments in a pole distance and analyzes the fluctuation law of end electromagnetic force, to provide a reference for the end windings structure of the motor. This method has the advantages of high computing speed and flexible application.