Aiming at the problems that the effective contact area between the steel bar and concrete decreases and the bonding property becomes worse after the reinforcement is bundled, the bond anchorage property of the rein? forcement was studied through the bond anchorage tests of 57 pull out specimens and 6 beam specimens. The influ? ences of the number of rebars, test method, diameter of rebar, strength of concrete, anchorage length and the position of rebar on the bond slip performance of the bundled bars were studied. The test results show that the greater the num? ber of parallel bars, the lower the nominal bond strength; Compared with a single steel bar, the test method, anchor? age length, diameter of steel bar, concrete strength and position of steel bar have a similar influence on the bond strength of bundled bars, but the influence degree is different. Based on the test data analysis on the empirical for? mula of bond strength in design codes, it is suggested that the equivalent diameters of 2 and 3 bundled bars should be 1.41 and 1.73, respectively, so as to be used for the values of anchorage length and thickness of cover. When the thickness of cover is reduced, the anchorage length of the bundled bars can be appropriately extended.