Multidisciplinary coupling rapid design and optimization of mechanical structure was researched, and multidisciplinary design optimization of diesel engine motion mechanism was proposed. The comprehensive performance of lightweight, thermal, vibration and kinematic were considered in optimizing the diesel engine motion mechanism. Aimed of lightweight, 3-D parametric model of crankshaft-connecting rod-piston were founded, and the performances of lightweight, vibration, thermal and kinematic was set as constraint. Based the theory of collaborative optimization, multidisciplinary design optimization of the diesel engine motion mechanism performed good results.