The disclosure is related to a system and a method for collision avoidance for vehicle. In the method, the system predicts multiple routes of an abnormal vehicle in a period of time according to historical data when a nearby vehicle receives an alert from the abnormal vehicle. A route potential pattern can be created when the system gets the historical data. The system also computes one or more available routes for the nearby vehicle based on its vehicle information. Every available route has its collision risk value. The system finally provides a recommended route with lower collision risk value when it considers a time of the abnormal vehicle reaches its great change, a time of predicting the nearby vehicle meets the range of route potential pattern, and a safe distance there-between.