With the continuous development of the cities, the traffic situation has gradually become a topic of concern. The concept of an intelligent transportation system has been proposed and developed. In the field of intelligent transportation, the traffic data has gradually increased. People have higher demands to real time data. The traditional data processing methods and tools have become unable to meet the needs of urban transport development. In this paper we analyzed the basic theory of granular computing, the methods, technology and current situation of granular computing. Besides, we discussed the hot issues of granular computing in an intelligent transportation system. Finally, granular computing in the development of intelligent transportation fields was also discussed.