Transition metal phosphides (TMP) have attracted wide attention as catalysts to drive the hydrogenation reaction. However, very few people are interested in regulating the crystal facet exposure intensity of Ni 12 P 5 catalyst to effectively improve the efficiency of hydrodechlorination (HDC) of trichloroethylene. Herein, we report that the exposure intensity of (3 1 2) high exponential crystal facet of the Ni 12 P 5 catalyst can be controlled by changing the chloride ion concentration. The correlation between the steps atoms generated during the growth of the (3 1 2) crystal facet and the active sites of the catalyst is evidenced through the hydrogenation of trichloroethylene at different temperatures. The consequence proved it is not positively correlated between the exposure intensity of (3 1 2) crystal facet and the hydrogenation activity. Catalytic activity first rises and then move down at different temperatures alone with the I (3 1 2)/I (4 2 0) ratio increase. The catalytic activity is the highest at I (3 1 2)/I (4 2 0) = 15.6. Several different characterization techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and N 2 -sorption isotherms have been used to characterize the samples.