The invention relates to the technical field of hydropower station gates, in particular to a gate locking beam locking device and a gate locking method. The gate locking beam locking device comprisestwo parallel rails arranged on platforms at the two ends of a gate groove and two groups of locking beams movably arranged on the rails, and further comprises locking devices arranged at the two endsof the locking beams respectively. Each locking device comprises an electric lead screw, an amplifying frame, a left supporting leg, a left connecting rod, a right supporting leg, a right connecting rod and rollers, the electric lead screw is arranged on the corresponding locking beam, the amplifying frame is arranged on the electric lead screw, the left connecting rod and the right connecting rodare hinged to the two sides of the amplifying frame respectively, the left connecting rod is hinged to the left supporting leg, the right connecting rod is hinged to the right supporting leg, and therollers are arranged at the bottoms of the left supporting leg and the right supporting leg respectively and movably arranged on the rail. Manual operation is reduced, the labor intensity of workersis reduced, the working efficiency is improved, the cost is low, and operation is safe and reliable.