An data-processing method was developed to obtain the device parameters from the resistance-voltage(R-V) characteristics measured in long-wavelength HgCdTe photodiode.This curve-fitting model includes the diffusion,generation-recombination,trap-assisted tunneling,and band-to-band tunneling current as dark current mechanisms.The fitting procedure was presented in details and the extents of the fitting errors were discussed.By fitting the R-V characteristics of a real device,the applicability of our method has been proved for obtaining the basic parameters of devices.