Abstract: The wind flow in underground coal mine is changing all the time. The coal mine ventilation network solution is a static calculation method, which can not solve the dynamic wind flow in real time, and requires wind speed sensor to obtain the dynamic wind flow data. However, the current wind speed sensor has poor stability and incomplete coverage. In order to solve the above problems, a real-time calculation method of mine ventilation network based on ultrasonic full-section wind measurement is proposed. The time difference between downwind and upwind of ultrasonic propagation between two points is used to measure the wind speed of the whole section of the roadway. The wind speed measurement result is independent of the sound speed and is not affected by the parameters such as the sound speed, temperature and humidity and air pressure. The problem that the air duct of the traditional wind speed sensor is easily blocked by mine dust is avoided. The resolution of the wind measuring device reaches 0.03 m /s. By continuously collecting the real-time working conditions of air volume and air pressure of main fans and the real-time air volume of some shafts and roadways, the ventilation network is calculated. And the fixed air volume method is used to integrate the monitored air volume into the ventilation network, and the real-time air volume of the whole ventilation network can be obtained through calculation. The Lagrangian multiplier method is used to correct and calculate the air volume and wind resistance in real time, so as to solve the problems of unbalanced air volume of nodes caused by redundant air volume monitoring branches and unbalanced air pressure of loop caused by fluctuation of the wind resistance. It is verified by an example that the calculation results of the real-time calculation method are highly consistent with the monitoring values. At the same time, the results strictly follow the constraints of the loop air pressure balance and the node flow balance. The real-time calculation of the ventilation network with 1 319 branches and 945 nodes in Ningtiaota Coal Mine is carried out. The time for one calculation is only 0.9 s, the number of iteration convergence is about 105, and the calculation results are continuously updated with time. The results verify the feasibility of the real-time calculation method.