DP600 steel sheet with high strength has drawn much attention in the automotive industry, but the shape change following forming and unloading has not been known widely. The time-dependent springback of DP600 steel sheet was investigated under different pre-strains by uniaxial tension. According to the viscous behaviors under the elastic and plastic loading tests, the lower limit of integration in the constitutive equation of linear viscoelasticity was modified and the creep compliance was gained from the creep curve at a constant stress level of 309 MPa at room temperature. The predicted curve was acquired by using the superposition of the unloading impulse and the historical loading curve. The results reveal that the strain rates with high initial values gradually decreased following unloading at room temperature. As the pre-strain went up, both the absolute anelastic strain of time-dependent springback and the anelastic proportion of the total springback increased. Meanwhile, the direction of the time-dependent springback was same as that of the initial springback and opposite to the loading direction. In the same springback period, the ratio of the unloading stress to the creep springback strain tended to vary more linearly with the pre-strain than those obtained from immediate unloading. The simulated results using the revised model are in good agreement with the experimental data.