Abstract：The traditional method of stability analysis on foundation pit is to calculate the minimum safety factor and to find the corresponding slip surface. This is easy in mathematics，but the depth and range in practical application are limited. The concept of space distribution of safety factor is an extension of the traditional analysis method in physics. The space distribution picture of the safety factor forms a series of potential slip surfaces，and every slip surface has one safety factor. In fact，The space distribution of the safety factor is indicated indirectly by the space distribution of the potential slip surfaces. This kind of expression can show the stability state of foundation pit directly，and can indicate whether there is any area which need to reinforce.
