An electrolytic sulfurization at room temperature has been introduced in the present work, which process parameters are optimized to the quenched Cr12 substrate. Morphology and microstructure of the sulfide layers are investigated deeply, and their formation mechanism is discussed in detailed. According to optimum parameter of sulfurizing process ( assistant current density of 1.8A/dm2, the saturated rare-earth-halide solution containing 300g Na2S2O3, 60g KHSO3 and 1000ml H2O, 298K/20~40min), the ferrous sulfide coating was easily obtained on the quenched Cr12 substrate with a uniform thickness of above 10μm, no matter about the treated parts with the complex geometrical shapes. The tribological experiment results of a block-on-ring tribometer indicate that the sulfide coatings on hard substrate have a very low friction coefficient and could obviously reduce the wear extent of its counterpart. Compared with the traditional low-temperature process, this sulfurizing technology has such virtues as simple process, heatless, low cost, little deformation, without pollution question, etc., which could be employed for industrial solid lubricant due to the good friction-reducing characteristic of lamellar-structure FeS phase.