The spatial variability of seismic fields significantly impacts the seismic performance of power systems and gas systems (power-gas systems). To accurately address the impact of non-uniform seismic fields and the interdependence of system functions on power-gas systems, a bidirectional interdependent seismic connectivity reliability assessment model for power-gas systems is proposed. Taking the IEEE 30 power system and a 47-node gas system as examples, spatially non-uniform seismic fields are generated based on the attenuation relationships of seismic motion parameters. By integrating the seismic vulnerability model, the failure probabilities of components are calculated. The Monte Carlo method is used to simulate earthquake damage samples, thereby assessing the seismic connectivity reliability of the power-gas systems. The results show that within the spatial seismic fields, the power system components are more vulnerable, and the seismic connectivity reliability of the system is lower. The power system has a greater impact on the gas system.