For an innovative opposed-piston diesel engine (OPE) with two-stroke operation mode, it attracted even more attentions than ever in some developed countries all around the world, attributed to the unique advantages of higher power density that conducive to downsize IC engine, as well as the potential of further reducing fuel consumption for outstanding thermal efficiency. To achieve fast practical application and ensure the feasibility in concept design stage, the performance characteristic of OPE crankshaft system was investigated, and thus a theoretical analytic model of crankshaft system in an OP2S (Opposed-piston two stroke) engine was established. The effects of all structural design variables on averaged output torque of OPE crankshaft were analyzed, respectively. It was found that the initial crank angle difference between inner crank web and outer crank web was considered as a most critical contributor to boost the averaged torque output than other design variables. The related 3D model of crankshaft was updated automatically on the basis of the optimized results. Eventually a prototype of unique OPE crankshaft was processed and bend fatigue testing was carried out in laboratory. Based on S-N Curve the HCF (High Cycle Fatigue) calculated results showed that the minimum safety factor on crank journal fillet can meet relevant evaluation criterion.