The accurate reconstruction of civil aircraft gust load is of great significance to flight safety.A reconstruction method of dynamic gust load is studied based on the stochastic optimization algorithm. Firstly, based on the aero-elastic coupling equation in the frequency-domain, a time-domain analysis model of the dynamic gust load is established. Secondly, the profile of the gust field is parameterized by Hicks-Henne bump functions. In order to match the measured target values, the parameters of each bump function are optimized based on the stochastic optimization algorithm. Then, the reconstructed profile of the gust field is obtained, as well as the time history of the corresponding dynamic responses and loads. Finally, numerical simulations of the Generic Transport Aircraft (GTA) model experienced the 1-cos shape gust is carried out. The results show that the method established in this paper can be used to recognize the profile of the gust field, and reconstruct the gust dynamic loads. In the numerical examples, the maximum load factor error is 3.5%, and the maximum load error is smaller than 1%.