An aeroelastic trim of a coaxial rigid rotor with lift-offset was developed and applied to analyzing the lower harmonic load of coaxial rigid rotor. The structural dynamics model and the double-rotor aerodynamics model were jointly used to develop the coaxial rigid rotor’s vibration load computing method. The lower harmonic load of blade root flap bending moment and blade root lag bending moment were analyzed in detail the influence of advance ratio, rotor speed and lift offset. were cowsidered the results show that the predominant 2/rev trend in blade root flap bending moment and edge bending moment at high advance ratio, and the predominant 1/rev trend in blade root flap bending moment at high lift offset, the edge bending moment would be suppressed at high lift offset.