Considering the randomness of input variable used in flight load calculation, the Monte Carlo simulation and the variance-based global sensitivity analysis method were employed to analyze the uncertainty and the corresponding global sensitivity indexes of horizontal-tail load for acute pitch maneuver. In the paper, the influence of aerodynamics and center of gravity(CG) uncertainty, as well as global sensitivity analysis on the horizontal-tail load were presented. The results of uncertainty analysis show that the horizontal-tail load due to angle of attack(AOA) is sensitive to the input uncertainties. From the results of global sensitivity analysis:1)the horizontal-tail load due to elevator is only influenced by the elevator control effectiveness; 2) the tail-off pitching moment coefficient with zero AOA and the CG have mainly influence on the horizontal-tail load due to AOA; 3)the elevator control effectiveness has the most influence on the total horizontal-tail load, and the tail-off pitching moment coefficient with zero AOA and CG has the second. The validity of the proposed method has been validated, which are useful for promoting the calculation precision of flight load in aircraft design.