Mobile lifting jack is one of the important equipment to CRH train overhaul, mostly in the manual mobile lifting jack. The JC-17B mobile lifting jack is often used as a lifting jack of CRH, which can implement lifting operations of 8 and 16 trains simultaneously. The mobile lifting jack mainly consists of the rack, transmission device, head supporting portion, walking device and other components. For efficiency, some structural modifications have been carried out, with electric pushing rods used for the expansion and contraction of the head supporting portion, and motor drive used for the walking device. At the same time, the original motor has been modified from the traditional top installation to the bottom installation to facilitate the maintenance of the lifting jack. Rack as an important component bears all loads, and its mechanical properties, especially the strength, play an important role in the normal operation of the entire equipment. This is the use of modern design method, using Pro/E, ANSYS and other modern engineering software platform, to do mechanical and modal analysis for rack on JC-17B mobile lifting jack, complete the rack design optimization, The analysis results show that the maximum stress is, which does not exceed the yield limit. Additionally, the thickness of the rack is reduced by 2mm, and the mass is reduced by 21.9%, thereby having saved materials and reduced production costs. Practice has proved that the mobile lifting jack developed based on the optimization method in this paper works well in actual operation, and for the future of all types of mobile lifting jack development, technological transformation and equipment renewal provides a reliable basis for the design.