According to the big flow characteristics of heavy duty diesel engine, the accumulator injector of common rail engine was designed. The CFD software was used to establish the multi-dimension two phase flow model of the fuel flow in the injector, and then the influence of accumulator parameters to fuel flow in injector was researched and analyzed. The results indicate that as the increasing of section area of the restriction orifice, the cavitation effect is strengthened, the flow rate is reduced and the discharge is decreased. As the cubage of the accumulator chamber is enlarged, the cavitation effect is strengthened and the fuel flow rate in injector orifice becomes slow.