Based on the dislocation density changes during deformation and deformation interval, a method of using the initial dislocation density before the deformation to describe residual strain is proposed. Double-hit compression tests are performed in X70 pipeline steel on a Gleeble-3500 thermomechanical simulator. Parameters of dislocation density model are obtained after the test data regression. The initial dislocation density after different time interval is calculated. The deformation resistance is also calculated from deformation resistance model. The good agreement between the predicted values of deformation resistance and experimental results indicates the validation of the computational method. As static recovery is dominant when the interval time is short, it is necessary to take the static recovery into account when calculating residual strain. It can only take static recrystallization into consideration when the interval is long. The method of this study is based on the formation mechanism of residual strain. It has a wider range of application and a better precision of calculation comparing with the traditional methods.