The invention relates to a bridge deck slab longitudinal unequal strength steel-concrete composite structure bridge and a construction method thereof and belongs to a novel bridge structural system applied to a continuous composite girder bridge or a composite rigid frame bridge. The bridge deck slab longitudinal unequal strength steel-concrete composite structure bridge of the invention is composed of super-high-performance concrete, ordinary concrete and steel beams. According to the ridge deck slab longitudinal unequal strength steel-concrete composite structure bridge of the invention, shear-resisting connection components and upper concrete plates are connected with each other so as to form an integrated body and work jointly, and therefore, the strength and rigidity of the bridge can be improved, and the quantity of steel consumption of the whole bridge can be decreased. The bridge deck slab longitudinal unequal strength steel-concrete composite structure bridge of the invention has respective advantages of an ordinary composite bridge deck system and super-high-performance concrete, and the advantages of high strength, high rigidity, excellent anti-cracking performance, high durability, easiness in construction and the like, and has a broad application prospect in composite structure bridges on which negative moment regions exist, such as a continuous girder bridge and a rigid frame bridge.