Based on microgravity monitoring technology, natural gas occurrence characteristics of Y21 gas storage was predicted, which was rebuilt from abandoned gas reservoir with strong edge and bottom water flooding in China. Through microgravity data collection in the study area and forward modeling based on geological models, the variation range of gravity values caused by fluid density change in the gas reservoir was defined, the residual gravity anomalies of the injection-production layer were extracted and analyzed, and the fluid enrichment characteristics in the injection-production layer were finally predicted, providing technical support for the optimization of the injection-production program of the gas reservoir. The results of the first microgravity measurement and processing show that the natural gas rich area in the gas storage is located at the high point of the structure, which is basically consistent with the geological structure and the expected charging effect of the gas storage.