This paper investigates the influence of thickness and minority carrier lifetime of multiplication layer and absorption layer on dark current, based on InGaAs/InP avalanche photodiode. Results demonstrated that the thickness of absorption layer mainly affects shockley-read-hall (SRH) and trap-assisted tunneling (TAT) dark currents, while the thickness of the multiplication layer mainly affects TAT and band-band tunneling (BBT) dark currents. The minority carrier lifetime, equivalent to the defects effect, plays a role in SRH and TAT dark currents. Analysis of dark current mechanisms could provide a well theoretical prediction for avalanche devices with low dark current and high signal-to-noise ratio.