The invention discloses a continuous arch bridge reinforcing method based on reduction of horizontal thrust of arch supports of an arch bridge. Reverse arches are arranged below arch ribs of main arch rings of all spans of the continuous arch bridge, the reverse arches and the arch ribs are connected through diagonal web members, the arch supports of the reverse arches are connected with the arch ribs through anti-bending embedded parts and anti-shearing anchor bolts, and accordingly the reverse arch structures used for reinforcing and the original arch ribs form a rigid restraining supporting system. The reduction degree of horizontal thrust of the arch supports of the arch bridge in the rigid restraining supporting system has a close relationship with seven parameters of the arches to be reinforced and the reverse arches. By setting different variable values of the seven parameters, the ratio of the horizontal thrust of the arches to be reinforced to the horizontal thrust of the arch supports of the reinforced arches serves as a moment variation token state, and a relational expression of the seven parameters and the moment variation token state is obtained based on the finite element parameter analysis fitting method. By applying the continuous arch bridge reinforcing method, the structural characteristic internal force value can be worked out by combining with the relational expression, and accordingly reverse arch reinforcing is conducted through the optimal scheme.