Due to the difference of movement and boundary conditions between long-primary double-sided linear induction motors (DSLIMs) and short-primary DSLIMs, the longitudinal end effect is different. This paper analyzes the dynamic longitudinal end effect of long-primary LIMs according to the basic principle and electromagnetic field theory and explains the difference of magnetic field traveling wave and its influence between these two kinds of DSLIM. The equivalent circuit model and correction factors considering the end effect are described through theory analysis. To verify the validity of the model, 3-D field analysis by Ansoft 3-D is implemented, and the field distribution is presented. The analysis results have a good agreement with the results where the end effect is considered than that where the end effect is not considered. A useful conclusion is that, with proper selection of the secondary poles and proper attention to the slip that the machine is operating at, the end effect will have a much smaller influence than that in the short-primary DSLIM. It provides a good way for this kind of machine design and industrial application in the future.