A calculation research is conducted on the wind tunnel test of tie-down aerodynamic load for civil aircraft in a low speed wind tunnel based on numerical wind tunnel technique. The numerical model of aircraft model and wind tunnel test section is developed by CFD software. Cases are solved under the condition of -180°≤β≤0°while the boundary condition is set according to the wind tunnel test parameters. The calculation results can agree well with the test results since the tunel wall and ground are considered in the model. As -120°≤β≤-90°, tiedown device on front landing gear bears comparablely large loads which consists of: longitudinal load resulted from the upward pitching moment created by horizontal tail part and rear fuselage, and lateral load resulted from yawing moment. Cl is less than Cm by 2 orders of magnitude, which hardly affects the tie-down load analysis. Tie-down load can be alleviated by pre-deploy the horizontal tail part, rudder or elevator. The study could provide a reference for numerical modeling study for civil aircraft in low speed wind tunnel test.