In traditional semi-rigid analysis of extended end plate connections is assumed to be deterministic parameters, most of moment-rotation models of the joint is determined by curve-fitting and statistically regressed with the test data. Those parameters of the models have little physical meanings and the effect of correlations between parameters is neglected. This paper deals with a semi-rigid joint of extended end plate connections based on correlation and sensitivity analysis. A numerical study was carried out and the finite element analysis was validated compared with the experimental results.The relative moment-rotation model was concluded based on correlations in parameters and probabilistic sentivity analysis. The relationship between height and width of steel beam was partial correlation, the relationship between thickness of steel beam flange and thickness of steel beam web was partial correlation. Height and width of steel beam, the distance of upper bolts to axle wire of steel beam were important sensitive parameters for the extended end plate connections.