In order to solve the rerouting problem of air traffic flow management (ATFM) in severe weather, a new rerouting method based on the improved artificial potential field model (IAPEM) is proposed. Aiming at the shortcomings of traditional potential field model, the potential field function has been improved. The additional gravitation point is introduced to remove the local minimum value. The ATC program and flight performance are considered. The linear fitting method is used, so the vibration and discrete points would be eliminated. The curve cut-off method is used to optimize the rerouting path by eliminating the extra turning points. The rerouting problem caused by thunderstorms in South west of China is simulated. The results show that the constrained areas can be avoided safely and effectively by using the proposed method, and the planning is swift and effective.