Abstract: The strengthening technique of external-bonded prestressed FRP plates and adjacent surface mounted FRP strips are all important techniques of strengthening a concrete structure with FRP. However, there are considerable limitations of the two techniques. It is attractive to develop the technical of adjacent-surface-mounted prestressed FRP strips, by combining the advantages of the above two strengthening methods, to further promote FRP applications in retrofit of concrete structures. In this paper, a total of 5 reinforced concrete beams strengthened with FRP was constructed and static load tests were conducted. The behavior and failure mode of specimens were investigated intensively, especially the specimens strengthened with NSM FRP. Furthermore, the difference of mechanical performance due to various strengthening techniques was shown through a comparison, and the effect of initial stress on the behavior and failure mode of specimens was analyzed. The testing results showed that the mechanical performance of flexural member can be improved significantly by strengthening with NSM prestressed FRP strips, and the improved effect was similar to that of the technical of EB prestressed FRP plates. The prestressed FRP strips can be anchored by epoxy through the method of adjacent surface mount. However, the failure modes of beams strengthened with NSM FRP strips were debonding of epoxy- concrete interface and tearing of concrete cover. Therefore, the further work of NSM prestressed FRP technique should be focused on the constructional method of improving bonding strength of epoxy-concrete interface and preventing tear of concrete cover.