This paper first derives the accurate computational formula of guidance electromagnetic force, when guidance magnet has the movement of the lateral excursion and yawing relative to the curved guideway. Firstly, the gap distribution characteristics between the guidance magnet and the curved guideway have been analyzed and simplified. Secondly, the theoretical formula of electro- magnetic force for singled magnetic pole has been derived by the air-gap magnetic permeance and flux tube methods. Then, the numerical calculations have been done by Ansoft Maxwell, and according to the numerical results, the theoretical formula has been modified accurately. Finally, the formulas of electromagnetic resultant force and resultant moment for guidance magnet have been represented, and the variation curves of electromagnetic force changing with maglev line indicate that gap changes caused by curved guideway should not be neglected. The formulas acquired in this paper are in favor of dynamics modeling and controller design for guidance system, and analyzing the running states of magnet and the curved form of guideway influencing on guidance system.