In order to improve the calculation efficiency of the obstacle limited takeoff weight calculation model of a domestic civil transport aircraft, its algorithm was studied in detail, and the reasons for the low calculation efficiency of the model were analyzed. On this basis, an optimized calculation model was established in combination with relevant civil aviation regulations. The obstacle limited weight, acceleration height and calculation time of the optimization model and the original model under different obstacles and different wind speeds were calculated and compared. The results show that the obstacle limited weight and acceleration height calculated by the optimization model are basically the same as those calculated by the original model; The original model uses the maximum acceleration height method to determine the obstacle limited takeoff weight, there are two unknowns: takeoff weight and maximum acceleration height, more iterations and longer calculation time; The optimization model adopts the method of minimum acceleration height, only the takeoff weight is an unknown quantity, which can shorten the calculation time and greatly improve the calculation efficiency on the premise of ensuring the accuracy of the calculation results; While calculating the take-off flight path, judging whether the aircraft can cross the obstacles can reduce the calculation time ; The optimization model also has reference significance for the calculation of obstacle limited takeoff weight of other types of civil transport aircraft.