The invention discloses a loose broken tunnel top plate reinforcing and supporting method, and belongs to mine tunnel supporting methods. The method includes: spraying concrete on the surface of a loose broken tunnel top plate, adopting anchor bolt supporting and hollow anchor pipe grouting to support top plate surrounding rock, laying a steel fabric piece, and respraying concrete on a leveling layer; laying a flexible cushion layer appressed with the leveling layer, and reserving deformation amount between the flexible cushion layer and the leveling layer; and paving an anchor-tensioning support on the top plate. The anchor-tensioning support is composed of a pre-stressed anchor rope and multi-sections of corrugated steel web box-shaped beams, elastic connecting parts are adopted to connect adjacent sections, the anchor bolt/anchor rope penetrates through a reserved anchor hole anchoring rock layer on a pull rod, the whole anchor rope is pasted and applied with prestress, and the anchor-tensioning support is arranged parallelly along the direction of a tunnel. By the method, problems that the broken top plate is sunk greatly and supporting of conventional mining I-steel pull rods and flat steel box-shaped pull rods is quite prone to damages are solved, so that stability and safety of top plate supporting are effectively guaranteed, and economic benefit is evident.