We present the simulation results of the InGaAs/InP avalanche photodiode (APD). In the structure a 70 nm InGaAsP grade charge layer and a 70 nm InP charge layer between absorption and multiplication layer have been used for reducing the dark current and achieving higher avalanche gain. A 50 avalanche gain around 35 V breakdown voltages has obtained, which has enhanced by nearly 4 times than that of the conventional InGaAs/InP APD. It has been also shown that the dark current in the device can be significantly reduced nearly one order compared to the corresponding conventional one. The numerical simulation means may design the high gain and low breakdown voltage InGaAs/InP APD.