Data regarding the adsorption-sensing characteristics of two-dimensional (2D) materials are crucial for guiding their design and use in gas sensors. XSb (X = Si, Ge, Sn) are novel 2D materials anticipated to exhibit thermodynamic stability and have the potential for experimental production. Nevertheless, the adsorption- sensing characteristics of XSb (X = Si, Ge, Sn) monolayers have not been thoroughly examined until now. This study employs density functional theory (DFT) and non-equilibrium Green's Function (NEGF) approaches to systematically investigate the structural, electrical, and adsorption-sensing properties of XSb (X = Si, Ge, Sn) monolayers for gas molecules H2O, CO, SO2, and NO2. This work provides a novel analysis of the adsorption- sensing characteristics of 2D XSb (X = Si, Ge, Sn) materials and offers recommendations for developing NO2 gas sensors utilizing these materials. Specifically, our findings suggest that the SnSb monolayer is a promising 2D sensor material for detecting NO2 gas with high sensitivity.