Perfluoroisobutyronitrile (C4F7N) is a new type of eco-friendly insulating gas widely used in various gas insulation systems. An effective method for diagnosing the operational status of insulation equipment is to design gas sensor materials to detect C4F7N breakdown products. Using density functional theory, we investigated the sensing ability of the Pt3 cluster doped SnS2 monolayer for common C4F7N decomposition gases (CF4, COF2, C2N2, and CF3CN). We explored the adsorption energy, charge transfer, adsorption distance, and density of states of the Pt3-SnS2 monolayer as a C4F7N breakdown gas sensor. The results indicate that the doping of Pt3 clusters has a relatively small improvement in the adsorption capacity of CF4 and COF2 gases, indicating physical adsorption, but a significant improvement in the adsorption capacity of C2N2 and CF3CN gases, indicating chemical adsorption. This work provides additional potential applications for Pt3 cluster doped SnS2 monolayer gas sensing materials.