The invention discloses an anti-collision method and system under different vehicle conditions, and belongs to the technical field of vehicle safety. The method includes the steps that the vehicle conditions are judged according to the vehicle speed and the corresponding safety distance, and the trajectory calculation quantity, the trajectory computing cycle, and the information sending cycle are determined according to the different vehicle conditions, vehicle trajectories are calculated according to the trajectory calculation quantity, the trajectory computing cycle and vehicle running states, the vehicle trajectories are periodically broadcast, anti-collision detection is conducted through the comparison between the vehicle trajectory of one vehicle and the vehicle trajectories of other vehicles, and if it is detected that a collision possible occurs, an early warning signal is output. The anti-collision method and system under the different vehicle conditions can achieve distinguishing of different risk levels of the vehicles through a vehicle condition determination strategy, targeted anti-collision warming for dangerous vehicles can be conducted, information transmission amount can be reduced through scattering the trajectory calculation to each vehicle, the decision making early warning speed test is improved, the occurrence of the vehicle collision is effectively prevented, and traffic accidents are reduced.