In view of the fact that the mean method is not sensitive to road congestion changes for the existing traffic evaluation methods, this study proposes a congestion ratio evaluation index based on real-time traffic con- dition data. Firstly, the GIS analysis and processing software was used to classify the traffic information of the real-time road condition data, and the change state of each road in a certain period of time was evaluated ac- cording to the classification value of the road condition change. Based on the traffic data of different working pe- riods in five working days in Nanjing, the ratio of congestion to traffic congestion was calculated. According to the calculation results, the spatial and temporal distribution characteristics of congested roads in Nanjing working days were analyzed and evaluated, and some feasible suggestions for avoiding blockage and slow blocking were put forward. It maintains that the evaluation method can be applied to urban traffic operation analysis and road congestion change analysis.