The invention discloses a prefabricated cable groove-based high-speed railway bridge decking structure and a construction method thereof, and belong to the technical field of high-speed railway bridgedecking structures. The high-speed railway bridge decking structure comprises a prefabricated beam, prefabricated shielding plates, protective walls and prefabricated cable grooves with U-shaped sections, wherein the prefabricated shielding plates are arranged at the edges of the prefabricated beam in the direction along with a bridge and are arranged at intervals in the direction perpendicular to the bridge, the protective walls are arranged on the inner sides of the prefabricated shielding plates in the direction along with the bridge, the prefabricated cable grooves are arranged between the prefabricated shielding plates and the protective walls in the direction along with the bridge, and grooves for pouring vertical walls are formed between the prefabricated cable grooves and the prefabricated shielding plates. According to the structure and the method, the driving safety of a beam transporting vehicle can be improved, the service life of the structure can be guaranteed, the construction efficiency can be improved, the mounting method of the prefabricated cable grooves is simple, and the construction quality can be guaranteed more easily.