A predicting method of car accident severity which uses a predicting device of car accident severity to analysis the picture change level of a dashcam video, and when it determines there has a car accident happened in the dashcam video, the predicting device of car accident severity gets a time of the car accident and at least one environment feature from the dashcam video, and recognizes the objects in a video footage of the dashcam video which was recorded in a period of time that from the time before the time of the car accident to the time after the time of the car accident, and determines the object that the car collided. The predicting device of car accident severity predicts a severity degree of the car accent according to the history data which records car accent severity degrees and their corresponding environment features and collided objects provided by the Police unit and the at least one environment feature and the collided object which was determined. |