The invention discloses an inertia locking mechanism for a seat. The inertia locking mechanism is characterized by comprising an inertia locking mechanism body which is used in a combined structure of a rotating part and a fixed part in the seat, wherein the rotating part is hinged to the fixed part; the inertia locking mechanism body is installed on the fixed part. During collision, the inertia locking mechanism body locks up the rotating part by the aid of inertia, and on normal condition, the inertia locking mechanism body does not lock up the rotating part without affecting rotation of the rotating part. The inertia locking mechanism can solve the problem that the one-sided medium and low strength angle-adjuster seat is insufficient in strength in front-back collision test, a stop piece cannot interfere turnover and use of the seat in the normal use process, and the inertia retaining piece cannot cause shaking and abnormal noise. The cost of the inertia locking mechanism is only 25%-30% of that of the conventional scheme.