Residual displacement is one of the most important parameters to assess the repairability and usability of bridge structures after an earthquake, while the P△; effect has significant influences on the residual displacement of bridge structures. Probabilstic characteristics and empirical prediction equations of residual displacements for bridge structures were quantificationally investigated based on large numbers of nonlinear time history analyses by taking the P-△; effect and randomness of strong ground motion into account. The governing differential equation of motion for bridge structures including the P△; effect was developed firstly based on the dynamic balance theory. The influences of the P-△; effect, the post-yield stiffness ratio, the normalized yield strength and the natural period of vibration on the statistical characteristics of residual displacement were quantificationally investigated based on the inelastic dynamic responses of bridge structures under 69 selected strong ground motions. The correlation between the peak and residual displacements was discussed and the prediction equation for the residual-to-peak displacement ratio was also proposed. The results show that the P-△; effect, the post-yield stiffness ratio and the normalized yield strength have significant impact on the mean of residual displacement; the residual displacement can be described as the Lognormal or the Weibull distribution variable; the correation between the residual and peak displacements was remarkable and the mean (dispersion) of the residual-to-peak displacement ratio increases (decreases) with the increase of the natural period of vibration and the stability factor.