Abstract: Traditional model description languages can not satisfy the needs of product model description in virtual prototype based conceptual design （VPBCD）. Depending on the improved bond graph and V desModel model, a novel model description language-virtual prototype modeling language （VPML） is presented. VPML is a discipline and process independent model description language for electro mechanic products in VPBCD. VPML has strong abilities of geometry and behavior modeling, and provides coherent model description for cooperative design, concurrent design, and confederate simulation of multi discipline systems. By employing the inner algorithms of virtual feature generation, VPML can also solve the insufficient information problems in constructing the virtual prototype during conceptual design phase.