Abstract: In order to greatly improve the flexural capacity of the existing reinforced concrete beams andavoidwet concrete operation, a method of strengthening rigid concrete beams with double-sided channel steel is proposed. The effectiveness of the method was analyzed by comparing reinforced specimens with five different connecting methods and one specimen without strengthing. The bending bearing capacity, ductility and failure morphology of each specimen were tested. Different calculation methods were analysed to compare the accuracy of calculating the flexural bearing capacity of the specimen. The results showed that: 1) after the reinforced concrete frame beam was strengthened with bolted double-sided channel steel, the flexural bearing capacity of the frame beam wass greatly improved; 2) the reinforced concrete beam specimen was strengthened with bolted double-sided channel steel and the flexural capacity was 73%~78% of the flexural capacity calculated according to the steel and concrete composite beam design method in Design Standards for Steel Structures (GB 50017—2017); 3) the flexural bearing capacity of the reinforced concrete beam specimens strengthened with bolted double-sided channel steel was 1.21~1.28 times of the flexural bearing capacity calculated according to the superposition method in Technical Specification for Steel Reinforced Concrete Structures (YB 9082—2006); 4) the measured flexural bearing capacity of the reinforced concrete beam specimens reinforced with side channel steel was 0.96~1.01 times of the flexural bearing capacity calculated according to Design Code for Composite Structures (JGJ 138—2016) after considering the influence of the stress distribution of the built-in steel frame, and this was quite reasonable.