The invention discloses an ADAMS-based automobile back door opening force analysis method, which comprises the following steps: 1) inputting a hard point coordinate, a pneumatic stay bar characteristic curve, back door assembly information, rotational inertia and a three-dimensional digital model of a back door assembly into ADAMS software; 2) establishing a dynamic model: carrying out constraintlimitation on a connecting part in the back door assembly; 3) establishing measurement: sending a motion instruction to the back door to enable the back door to rotate at a constant speed by taking the hinge as a rotating shaft; Setting collection points of a plurality of angles, and in each angle state, obtaining a moment at the back door mounting hinge; 4) taking the angle and the torque as two-position coordinates to obtain a door opening angle torque curve, and finding out the maximum torque Imax and the corresponding angle Theta*; And 5) calculating the opening force Fmax = Imax/L. The method can quickly, efficiently, scientifically, reasonably and accurately analyze whether the opening force of the back door meets the requirement or not, and provides a judgment basis for automobile design.