The zero-bias resistance area product (R 0A) and the saturation current density J 0 are both key parameters to give an indication of photodiode performance. In this study, an effectual experimental method to study the minority carrier diffusion characteristics of Hg ~1-xCd xTe photodiodes was presented. By I-V tests in a variational magnetic field B, R 0A and J 0 measurements were carried out as a function of B in the alloy composition range 0.5 < x < 0. 6. Based on the test results,the minority carrier diffusion length of shortwavelength infrared ( SW IR) HgCdTe photodiodes operating at room temperature was calculated. The value is in agreementwith the scale measured by laser beam induced current (LB IC)method.