The invention discloses a steel-UHPC precast slab combined bridge deck structure and a construction method thereof, and belongs to the technical field of bridge structures. The combined bridge deck structure comprises a steel bridge deck, UHPC precast slabs, PUE padding and wearing layers, wherein the plurality of UHPC precast slabs are arranged and are laid on the top surface of the steel bridgedeck at intervals, a plurality of stepped holes with large upper parts and small lower parts are formed in the UHPC precast slabs, and the UHPC precast slabs are tightly connected with the steel bridge deck through penetration of connecting pieces with pre-tightening functions in the stepped holes; the PUE padding is connected in joints between every two adjacent UHPC precast slabs in a sealing mode; and the wearing layers are laid on the top surfaces of the UHPC precast slabs and the top surface of the PUE padding. According to the combined bridge deck structure, the UHPC precast slabs are laid on the steel bridge deck, the tight fit between the UHPC precast slabs and the steel bridge deck is realized through the connecting pieces with the pre-tightening function, adverse factors such asvibration, impact and noise caused by the existence of the gaps among the UHPC precast slabs and the steel bridge deck under wheel loads are avoided, and the usability and the durability of the structure are improved.