A design method for an inerter with adaptively adjusted inertia ratio is based on a lead screw-flywheel inerter, which is to change the positions of mass blocks on a flywheel along the radial direction of the flywheel, so as to change of the moment of inertia of the flywheel, and thus to realize adaptive adjustment of the inertia ratio of the inerter. Specifically, the change of angular velocity of the flywheel is caused by the change of an external force load on a lead screw, a centrifugal force on the mass blocks in spring-mass block structures is changed by the angular velocity, and the positions of the mass blocks in the radial direction of the flywheel is determined by the balanced relation of the centrifugal force and a spring restore force, so that the design purpose is achieved.