Three same 7 m span reinforced concrete T-beams were strengthened with an external prestressed strengthening technique. CFRP (carbon fiber reinforced polymer) sheets were not affixed to the beams, but laterally pulled by WSGG (wave-shaped-gear-grip) anchor and gripped at the bottom or two sides of the beams. Two beams were strengthened at two sides, while the other one beam was strengthened at bottom. The flexural propterty test results indicate that the section of the CFRP sheets can be adjusted according to the moment of the beam and the high-strength properties of CFRP materials can be efficiently used. There is no difference in improving the flexural rigidity of the beams either strengthened at two sides or at bottom. The WSGG can anchor the prestressed CFRP sheets well. Based on the test results, we proposed an equation for calculating ultimate load and deflection of beams which are strengthen by externally unbonded prestressed CFRP sheets, and a flexural capacity formula according to the beam plastic hinge zone length limit state of the strengthened beams. And the formula for calculation deflection is derived by considering secondary effects of inertia. Compared with the experimental results, the above formulas are verified and can be used for design.