For hollow slab bridge, its concrete hinge joint is prone to be damaged under overload vehicles, as weakens the transverse integrity of bridge, leads to single slab bearing and threatens the safety of service. Aiming at the problem, a strengthening experiment of an actual concrete hollow slab bridge, which has experienced a destructive test with its transverse connections seriously damaged, was performed by applying external transverse prestressing to it. The strengthening design and construction technology of external prestressing were introduced. By means of truck static load test, the variation of deflections and strains of the bridge before and after strengthening under different tension force was obtained, and the influence of tension value to strengthening effect was emphatically analyzed. The test results proved the effectiveness of the strengthening method and some improvement suggestions were also presented.