Abstract: In order to solve the quantitative analysis problems of lane-changing influence on traffic safety, a Virtual Desire Trajectory of lane-changing is constructed based on the vehicle and driver's behavior characteristics. By combining 4 types of collisions caused by lane-changing, a safe operation judgment equation and restriction equation are respectively built in the vertical and horizontal direction. And the sensitivity of vehicle speed and lateral acceleration gradients to lane-changing safety is analyzed. Finally, an application example is given. This study shows that the changes of the lateral acceleration gradient have a direct impact on the safety of lane-changing.