The resistance factor in the draft version of Chinese Technical code for the application of fiber reinforced polymers in civil engineering for the shear-resistant design of reinforced concrete beams with U-wrap FRP strengthening is assessed from the probabilistic standpoint. The assessment using a resistance-factor-related computational uncertainty factor indicates that the average reliability indexes, for either unstrengthening or strengthening, increases at a slowing rate as load effect ratio increases from 0.10 to 2.5, and that the average reliability indexes for strengthened beams would dramatically decrease up to 19.2%~28.5% with the resistance factor specified in the code for U-wrap strengthening. A so-called reliability strengthening ratio is introduced to evaluate the change in average reliability index before and after strengthening with different resistance factors. A parametric study on this factor shows that if the reliability level in strengthened reinforced concrete beams is kept to be consistency with their corresponding unstrengthened beams, a value of 0.67 could be applied. The proposed relationship between reliability strengthening ratio and the resistance factor could be also used in personalized designs.