This invention is for the purpose of promulgating one kind of vehicle side collision caution system, it is mainly the establishment in an installment main body, this equipment this system includes photographic unit, the chassis sensing unit, the processing unit, the caution interface and so on, but its judgment processing flow including picks up the phantom step: Photographs the unit to pick up phantom of from the vehicle external environment, and this phantom information transmission to processing unit; Phantom analysis step: The processing unit picks up it by the photographic unit phantom of from the vehicle external environment, whether there is judges other thing existence, if has other things, and calculates stems from the vehicle and other things the relative velocity, the relative distance; Caution judgment step: Processing unit from vehicle with other things relative velocity, relative distance information, formula of by the preinstall, coordinates driving of condition from the vehicle, judges whether to propose the caution, if the caution again does not continue to carry on picks up phantom step and the phantom analysis step.