The invention discloses a rail traffic congestion degree calculation method and system. The method comprises the steps of calculating entry and/or leaving durations and transfer durations of passengers in a set line through passenger entry and leaving information in the set line of rail traffic and running information of a rail traffic tool in the set line; based on the passenger entry and leavinginformation, the entry and/or leaving durations, the transfer durations and the running information, calculating passenger capacity of the rail traffic in the set line; and obtaining a total seat number and rated total passenger capacity on the rail traffic tool, and based on the passenger capacity, the total seat number and the rated total passenger capacity, calculating a congestion degree of the rail traffic tool in the set line. According to the method and the system, the congestion degree of the rail traffic is calculated by considering the carrying capacity of the line based on data statistical analysis, so that a calculation result is more objective and accurate.