Shaximiao Formation gas reservoir in Zhongjiang Gas Field has great exploration and development potential. However, it is primarily characterized by ultra-low porosity and ultra-low permeability, with pronounced reservoir heterogeneity. Addressing the challenges related to the early-stage reliability of lithology and gas-bearing identification, as well as the accuracy of reservoir porosity and thickness predictions, a comprehensive seismic rock physics analysis was undertaken. The analysis focused on assessing the feasibility of reservoir prediction through forward modeling, fluid substitution, and rock physics scaling. The objective was to elucidate the specific relationship between seismic elastic parameters, lithological parameters, and reservoir parameters for gas reservoirs. By optimizing sensitive parameters related to lithology, physical properties, and gas-bearing properties, qualitative and quantitative prediction models for reservoirs were established. This entailed using attributes such as the maximum trough attribute, minimum wave impedance attribute, and the ratio of minimum longitudinal and transverse wave velocities to predict reservoir distribution. The lithology and gas-bearing property are identified by P-wave velocity ratio and P-wave impedance intersection. The shale content is quantitatively predicted by P-wave velocity ratio fitting or co-simulation. The porosity is quantitatively predicted by P-wave impedance fitting or co-simulation in sandstone. The gas saturation is quantitatively predicted by Lamda/Mu fitting or co-simulation in gas-bearing sandstone, which lays a solid foundation for the fine prediction of Shaximiao reservoir in the study area.