When the traffic volume is investigated, the traffic volume at the entrance and exit of the road section is not equal due to nonsynchronous observation time, observation errors or other reasons. However, in the study of OD matrix estimation, the traffic balance of the road section is required. In order to solve this problem, three methods for calculating the flow balance of road section were proposed, which were based on the simple and quick calculation, uniform flow distribution, and the reduction of flow change rate. MATLAB software was used to write the program to obtain the calculation results. What’s more, three evaluation indicators were proposed to verify the reliability of the balance calculation method. Finally, taking the actual road network consisting of three horizontal lines and three vertical lines as an example, the proposed method was used to calculate, and the proposed method was verified to be feasible and effective, when combined with the actual situation evaluation and analysis. The results can be used to route traffic distribution, and provide basic data for the traffic signal coordination control.