Abstract: In our report, based on the design of a collapsed deep foundation pit anchor cable in Guangxi, the control effects of prestressing force anchor cable’s force law on pile top displacement at different water levels were analyzed, the changes of anchor cable’s force with different prestressing force were studied, and then, the problems of foundation pit which collapsed caused by anchor cable invalidation were discussed. The results showed that there are some problems existed in the design load of deep foundation pit anchor, which should be consistent with the distribution of horizontal earth pressure, and the safety reserve design load of the upper anchor in deep foundation pit should be to improve, the function of prestressing force anchor in the pile anchor supporting structure can be greatly exerted, and which can improve the safety of deep foundation pit supporting. Our conclusion and suggestion can provide some references for the design of anchor cable in deep foundation pit.