Abstract: This paper analyzes the effects of aft-loaded empennage airfoil on the aircraft global trim through CFD (computational fluid dynamics) methodology, using MGAERO software and a basic fuselage-wing model of a typical civil aircraft of several different empennage modes. The calculation results indicate that the empennage of aft-loaded design would cause less loss of the lift and drag after the global trim of the aircraft, which would lead to some gains in the overall lift/drag ratio and aerodynamic performance with some combined effect such as twist. The theoretical evaluation of the gains is provided. This paper reveals the root cause of the trend that aft-loaded design is preferred for the empennage airfoil on the civil aircraft, and also shows that the overall drag including the trim part is important in the assessment of aircraft drag performance.