For the complexity and miniaturization of MEMS, MEMS design process is extremely different from general mechanical design process. Commonly the design flow is dominated by “trial-and-error” methods. It is necessary to describe design process of MEMS for reuse. This will help to reduce the number of redesigns and thus decrease the time to market. Based on XML and necessary extensions being made, a MEMS design process description language, called MDPDL, is presented and the syntax and implementation are discussed in detail. The Document Type Definition (DTD) is adopted to define the syntax rules for the tags of MDPDL, considering core activities and related resources of MEMS design process. Finally, an implementation case has been given out to illustrate the efficiency of MDPDL.