The results of high-density hydrogen plasma modification for HgCdTe long-wavelength n+-on-p photodiode arrays were presented in this paper. n+-on-p HgCdTe long-wavelength photodiode arrays with photodiode modified by hydrogen plasma immediately after B+-implantation were fabricated from a Hg1-xCdxTe/CdTe film grown by MBE. The maximum values of the dynamic resistance of the photodiodes in the arrays treated by hydrogen plasma were increased by one to two times compared with those of diodes without modification. The dynamic resistances of the diodes at larger reverse biases away from the maximum point of dynamic resistances were increased more significantly. Thus, it is obvious that hydrogen plasma modification was beneficial to the uniformity of operation dynamic range and detection performance of HgCdTe long-wavelength photodiode arrays because it can suppress the band-to-band tunneling currents and the trap-assisted tunneling currents in the diode.