The working process of a high power density(HPD)diesel engine was analyzed by computational simulation. Based on the analysis, the mechanical load on connecting rod of HPD diesel engine was calculated and the connecting rod stress distribution as well as its deformation under the highest load was analyzed by finite element method. The calculation results show that in varied running speed, the maximum compressive load acting on connecting rod of HPD diesel engine is 0.5~2 times higher than that of on connecting rod of traditional power density (TPD) diesel engine. The maximum stretching loads on the two engines are similar. The largest maximum compressive load does not occur under rated speed. The raise level of mechanical stress and the raise level of mechanical load acting on connecting rod basically shows a lineal relationship compared with