Abstract: To accurately assess the safety status of foundation pits and ensure their safe construction, this study conducted a time-series monitoring on key factors affecting the safety of foundation pits.Based on the Pair-Copula Bayesian Network (PCBN) model, which combines the flexibility of Pair-Copula in handling complex multivariate data with the advantages of Bayesian Network in dealing with uncertainty, a comprehensive reliability evaluation system has been established.This system enabled a quantitative assessment of the safety status of foundation pits, considering the complex correlations within monitoring data.The results indicated that there was a correlation between monitoring data such as vertical displacement at the pile top, horizontal displacement of the pile body, ground settlement, support axial force, and deep horizontal displacement of the pile (wall) body, and the Kendall's rank correlation coefficients all exceed 0.5 among them, indicating a strong positive correlation.The groundwater level was negatively correlated, however relative weak, with vertical displacement at the pile top, horizontal displacement of the pile body, ground settlement, support axial force, and deep horizontal displacement of the pile (wall) body, and the weakest correlation was found between groundwater level and ground settlement, with Kendall's rank correlation coefficient of -0.361 7.The PCBN model demonstrates good accuracy, the calculated reliability index β value is 4.056 for the deep foundation pit engineering of the Xintang Interchange section of the open-cut municipal tunnel, indicating that the foundation pit support structure is within the safe range.The research findings can provide an effective reference for the quantitative safety evaluation of deep foundation pit support structures.