Nuclear facilities generate large amounts of contaminated stainless steel metallic material during maintenance and decommissioning. As a new radioactive decontamination method, the self-brittle decontamination method has the advantages of fewer secondary contaminants and can be operated remotely mechanically. The addition of a certain amount of corrosive components to the self-brittlement composite decontaminant can achieve the dual function of self-brittlement and corrosion decontamination. The performance of the decontaminant was investigated by single-factor experiments using electrochemical tests, morphological observations, and weight loss tests. The results show that the decontaminant has good self-embrittlement. When the concentration of HCl is 2.50 mol/L, HNO3 is 3.50 mol/L, NaCl is 0.10 mol/L, and FeCl3 is 0.15 mol/L, the decontaminant is formulated to have the best corrosion and decontamination effect on stainless steel. The detergent will produce a uniform corrosion layer on the surface of stainless steel, and the average corrosion depth can reach 8.3268 μm.