The disclosure provides a method for calculating a passenger crowdedness degree, comprising: establishing a video data collection environment and starting collecting video data of passengers getting on and off; reading the collected video data of passengers getting on and off and pre-processing a plurality of successive image frames of the video data; identifying a human head according to the pre-processing result and taking the detected human head as a target object to be tracked by mean-shift; and judging the behaviors of getting on and off of a passenger in the area where the target object is positioned and determining the crowdedness degree of passengers inside a vehicle according to the numbers of the passengers getting on and off. The disclosure also provides a system for calculating a passenger crowdedness degree. The disclosure can effectively reduce the false detection, leak detection and error detection of the head top.