Due to the complex operating conditions of electric vehicles, it is expected that the high efficiency distribution of the driving machines coincide with vehicle frequent operating cycles. In this paper, to explore the distribution laws of the high efficiency region of interior PM machines, three interior PM machines respectively with larger saliency(Lq >> Ld), low saliency (Lq > Ld) and inverse saliency (Lq < Ld) are designed and analyzed comprehensively. Through finite element simulation studies, it can be concluded that all three machines are capable of a wide speed range. Anyway, due to the large saliency and low PM flux level, the machine with Lq >> Ld can achieve maximum efficiency in medium-high speed regions. Then machine with low saliency and inverse saliency machine can achieve maximum efficiency at moderate speeds. This study will provide guidance for electric vehicles owing complex cycle conditions to match the suitable interior salient PM machines.