The utility model discloses an internal gear model that gradually bursts at seams becomes appearance, including first external gear, second external gear, internal gear and bottom plate, wherein first external gear and second external gear pass through fixed axle coaxial coupling, the synchronous rotation, and the second external gear meshes with the internal gear mutually, and the second external gear drives the internal gear and rotates in step with first external gear, and the internal gear pin joint is on the bottom plate. Press from both sides between first external gear and the second external gear and be equipped with the backing plate, backing plate and interior gear connection, the backing plate rotates with the internal gear is synchronous. First external gear and second external gear pass through the support body to be fixed on the bottom plate, and the support body can carry out position adjustment through the fixing bolt at both ends, and the regulation stroke is 0.6 times of second external gear and internal gear modulus. The internal gear is the negative addendum modification gear. Beneficial effect: novel structure, compactness, convenient operation has solved the internal gear model that gradually bursts at the seams and has become processing and push up the problem of cutting the phenomenon demonstration.