There are many failure modes in the foundation pit engineering. Considering the correlation between failure modes

the range of system failure probability is large using the Breadth Border method or the narrow bounds method. The response surface is established by using the uniform test and nonparametric regression method. On this basis

in order to obtain the index of each failure mode

the random parameters generated by the Monte Carlo simulation are interpolated. Combined with the Pearson correlation coefficient

the correlation is tested between failure modes. Considering the correlation of multiple failure modes

the system reliability analysis method of foundation pit engineering based on conditional probability is put forward. As a typical example

a system failure probability of foundation pit is analyzed by using the conditional probability method. A case study shows that the method is simple and reliable in calculation

so as to provide a new way for the system reliability theory of foundation pit.