Recent reports on the electrical properties of two-dimensional (2D) boron phosphide (BP) monolayer exhibits that it is expected to be used for nanoscale device. Here, we investigate the adsorption of hydrogen sulfide (H 2 S) gas molecules on pure and doped BP monolayer systems with first-principles calculations to exploit their potential applications in gas sensing. Our results predict that H 2 S gas molecules show stronger adsorption interactions on impurities-doped BP over the original BP monolayer. Both boron (B) and phosphorus (P) substitute doping methods are considered. Al-doped BP (Al-BP) shows the highest sensitivity to H 2 S, but P replacement Al-BP is more suitable as a sensor for H 2 S due to the moderate adsorption energy. Moreover, the B and P vacancy defects are also considered. Furtherly, analysis of band structure, the charge density differences (CDD), and density of state (DOS) show a positive change of electronic property when H 2 S gas molecules adsorbed on pristine/doped BP monolayer. This work explores the possibility of BP as a superior sensor through introducing the appropriate dopant and vacancy defects.