Abstract: The sine-sweep vibration test is one of the important ways of determining the dynamic properties of spacecraft structures in the low-frequency domain. The test data can also be used for the modification of finite element models. However, the sine-sweep vibration is not in a steady state, therefore, the structure responses might be different from those under the steady state, leading to errors in the model modification. Several numerical integration simulations are made to determine the influence of the sweep rate on the structure responses for a single-DOF system. It is found that under the sine sweep excitations, the maximum response value decreases with a shift of the peak frequency. Then, a non-dimensional sweep parameter η is proposed, and the correlation of the structure response with this parameter is obtained. The relational expression can help for the selection of a rational sweep rate before the vibration test, and also for the correction of the responses after the test.