Abstract: The reinforced concrete double arch bridge used for more than 35 years has been damaged severely and in very poor condition. Based on the safe evaluation of the bridge, the strengthening design is carried out. By means of enlarging the section of main arch lab, strengthening the spandrel arch, repairing the deficiency parts and planting bar technique, the carrying capacity and durability of the bridge for higher load class is improved largely. The method and the strengthening design described in the paper could be a valuable reference for the similar works.