To analyze mechanical performance and failure modes of continuous beams strengthened with BFRP and CFRP, flexural tests were conducted on one comparative continuous beam and seven RC continuous beams strengthened with the two types of fiber. The method of externally bonding fiber sheets on slab along sides of column to avoid column in hogging moment area of beam was applied. The results show that bearing capacity of beams strengthened with BFRP is less than beams strengthened with CFRP, except for ductility，in same condition. Allowable tensile strain of domestic BFRP is suggested as a fixed value of 0.007 for general flexural members, 0.01 for important flexural members. BFRP is a suitable strengthening material for flexural members demanding comparatively low improvement of bearing capacity, better ductility and corrosion resistance in rehabilitation and retrofit projects.