The presence of confined gas bubbles in gas-bearing strata alters soil properties, which poses safety hazards to ocean engineering. This study investigates the quantitative relationship between gas content and electrical conductivity and aims to identify shallow gas strata and mitigate associated risks accurately. Despite the recognized sensitivity of electrical parameters to gas-bearing characteristics, the absence of robust quantitative models correlating volumetric gas content (θ_g) with bulk conductivity (σ) remains a fundamental limitation in geophysical prospecting. A novel test vessel integrating consolidation and electrical testing is developed to address this critical gap. Using indoor remodeled gas-bearing fine-grained soil as the research object, the electrical conductivity of soil samples with varying initial gas contents is measured using the quadrupole electrode method. The effect of gas content on microstructure was analyzed in conjunction with scanning electron microscopy (SEM). This study showed that conductivity nonlinearly decays with increasing gas content, showing a sharp decline of 12.3 mS/m from the initial 5.04 % gas increment (53 % water content), with attenuation rate progressively decreasing. SEM showed that the particle contact shifted from face-to-face contact to edge-to-side contact with increasing gas content, and the number of pores, volume, and nonhomogeneity increased significantly, which led to changes in the conductive network. A model for calculating the electrical conductivity of gas-bearing fine-grained soil considering the volumetric gas content was developed by introducing the volumetric gas content index σ = aθ_g^b (R² = 0.904∼0.994). The results of the study provide an important basis for identifying the gas content of marine gas-bearing formations, preventing related engineering disasters, and optimizing the development of shallow gas resources.