This paper investigates the longitudinal end effect of the line-start permanent magnet linear synchronous motor (line-start PMLSM), where conductive ladders embedded into the mover enhances line-start capability but induces the longitudinal end effect due to the eddy current. The longitudinal end effect is first investigated by virtue of analytical solutions of electromagnetic field. Then the coefficient of longitudinal end effect is simplified as piecewise functions for industrial applications, with which an algorithm is proposed to evaluate transient characteristics of the line-start PMLSM. The theoretical method proposed in this paper is proved effective and accurate by experiments.