The invention discloses a concrete structure reinforcing method based on near surface mounted prestressed FRP (Fiber Reinforced Polymer), which comprises the steps of: 1, slotting, arranging more than one preformed groove on a concrete structure to be reinforced; 2, installing a tensioning tool of an FRP strip and an FRP strip clamp; 3, tensioning internal FRP strips in the tensioning tool and the FRP strip tool so that the internal FRP strips are tensioned, placing the internal FRP strips in the preformed groove, filling an adhesive, keeping a clamping and anchoring state for a period of time and then curing; and 4, relaxing: when adhesive resin is cured completely to reach the strength, dismantling the FRP strip clamp. The concrete structure has the advantages of low cost, convenience for construction, long service life, good reliability and the like.