Yellow phosphorus tail gas is one of the most common industrial waste gases in Yunnan Province. The discharge of H2S and PH3 pollutants has caused serious harm to the environment. In this study, the simultaneous removal of H2S and PH3 by modified manganese slag slurry was investigated. The results showed that the highest simultaneous removal efficiency for H2S and PH3 was achieved after adding CuSO4. In order to investigate the relationship between catalytic activity and metal species, catalysts were characterized by FTIR, XRF, SEM, AAS, IC, and chemical element analysis. AAS and chemical element analysis results showed that the main active components of the catalyst were Mn and Cu ions. The catalyst structure changed over the reaction. The contact between the catalyst and H2S and PH3 was hindered by the metal agglomeration on the surface of catalyst, which resulted in the deactivation of the catalyst.