Abstract: Considering the randomness of Mach number and angle of attack, the non-intrusive polynomial chaos method is employed to analyze the uncertainty and the corresponding global sensitivity indexes of transonic aerodynamics for the NACA0012 airfoil. In the paper, the uncertainty analysis and global sensitivity analysis about the aerodynamic loads, flow field and the aerodynamic coefficients are presented. The results of uncertainty analysis show that the flow characteristics in the shock disturbance region and the boundary-layer separation region are sensitive to the input uncertainties. This is the main reason for the aerodynamic performance fluctuations caused by parameter uncertainties. From the results of global sensitivity analysis, the fluctuations of flow characteristics near the shock wave region are dominated by Mach number. Moreover, the coupling effect between Mach number and angle of attack is significant and cannot be ignored in shock disturbance region. However, this coupling effect is very weak from the results of aerodynamic coefficients.