In the common design of diesel engine, it’s necessary to optimize the engine in order to improve the dynamical characteristic and the fuel economic characteristic of the truck. The truck’s power balance equation was confirmed and verified by experiment，the dynamical characteristic and the fuel economic characteristic were analyzed based on the power balance equation and universal characteristic of engine. The results showed that the power utilization and the fuel economic characteristic were poor in the common cases. The optimized turbocharger and fuel injection pump for the diesel engine showed that the fuel consumption of 100km was reduced at the speed of 40～70km/h, and accelerating ability was improved. 