The significance is increasing efficiency and saving energy for segmenting the long primary linear motor into blocks. As the research object, the electromagnetic calculation model of the segmented long primary linear induction motor is established by using the finite element method (FEM), and the electromagnetic force computation of the motor is then derived from the virtual work method. The starting, operating and stalling process have been studied by ANSOFT, and the thrust, position and velocity curve are obtained coupled with the electromagnetic field distribution inside the motor. Finally, the change tendency of starting thrust is analyzed by using the FEM of Maxwell 2D, which is along with the variation of the air gap size, the interval of the primary and the starting position. The obtained calculation method can provide useful help for the optimal design and manufacture of the segmented long primary linear induction motor.