Cement mixing gravity retaining wall is widely used as a supporting method in soft soil area. It is not clear enough about the reliability analysis of gravity retaining structures in Shanghai region, and doubts about the mechanism of various factors still exist. By analyzing some practical projects collected in Shanghai, this paper discusses some problems on both the reliability levels and stability of gravity retaining wall. The influences of some factors such as the insertion ratio, the excavation depth and the width of wall on its stability are also evaluated. The results show that the safety level of practical projects is usually higher than requirements in the design code. In these typical stabilities, the sliding stability is usually judged as the controlling mode of stability checking. The security status of sliding stability and overturning stability can be improved obviously when the width and insertion ratio of the gravity retaining wall. In addition, the increase of insertion ratio contributes much more than the increase of the wall width in improving the security status of overall stability.