The invention relates to a TMIS traffic flow determination method and system based on cloud computing. The TMIS traffic flow determination method comprises the steps of (1) constructing a distributed storage resource pool on the basis of a cloud platform, collecting and storing monitoring data related to traffic flow calculation through a TMIS, (2) preprocessing the collected monitoring data through a concurrent processing framework, (3) writing a traffic flow calculation algorithm under the concurrent processing framework, utilizing static data for calculating the result of long-term traffic flow calculation, (4) utilizing the static data and dynamic data under the distributed environment for calculating the result of real-time traffic flow calculation corresponding to each station, and (5) providing a traffic flow calculation inquiry service externally through the cloud platform. The TMIS traffic flow determination system comprises a collecting layer, a storage layer, an engine layer, a service layer and a web service layer. According to the TMIS traffic flow determination method and system based on cloud computing, the cloud platform is utilized for obtaining various data required by traffic flow calculation in the TMIS, the concurrent computation is utilized for rapid data processing, and long-term and real-time traffic flow calculation and determination of railway transportation can be achieved.