To eliminate the edge breakdown and reduce the dark current of conventional InGaAs/InP avalanche photodiode, a novel avalanche photodiode with triple-mesa structure was proposed. The effects of edge distance, doping concentration and thickness of charge layer and multiplication layer on the device performance were systematically investigated by a commercial simulator. The simulation results shown that the device was possessed of low edge electric field and reasonable device size, when the edge distance was 8 μm. In this design, the high electric field was confined within the center of device and the breakdown voltage was improved. The edge electric field of optimized device was only 2.6×105V/cm, which was a half of central region at 40 V reverse voltage. What’s more, it can reduce dark current to 9.25 pA at 0.9 Vbr, which was only 1/3 for the dark current of traditional double-mesa avalanche photodiode.