Rapid product development relies heavily on quick and reliable design reuse. This paper analyzed the current design reuse research in mechanical product, pointed out the exiting drawbacks. It first presented the design reuse technology framework based on variant design for mechanical product. According to the characteristic of metal structure in crane, the four levels design reuse technology that plays a vital role in three dimensional variant design reuse including feature, component, assembly, and product was proposed. Design documents reuse including product design calculation and analysis report, 3D model, engineering drawing, Bill of material, process information gather table was also issued. A product design reuse platform has been developed based on crane design cases. The application system has validated the feasibility and practicability. It is able to shorten the time three times for achieving the 3D product model and engineering drawing, which has been carried out successfully in four crane manufacturing Company.