In practice, most wood beams to be repaired have already been damaged or degraded. It is necessary to study the structural performances of damaged wood beams reinforced by carbon fiber reinforced polymer (CFRP) sheets. Based on static tests of 8 damaged circular timber beams strengthened with CFRP sheets, bending behaviors are studied, including failure characteristics, ultimate bearing capacity, rigidity, and strain of timber section. The results show that CFRP sheets have a good strengthening effect for timber beams. The loading capacity of a timber beam reinforced by CFRP is effectively enhanced. The results are useful to practical design.