Abstract: Based on the results of 12 sets of pull-out tests of mortar specimens, the relationship between bond stress and slip is obtained to determine each and every phase of the failure process of anchoring bars, including microslip, crack-oriented slip, splitting, slip reducing and residual slip. The effects of mortar strength, anchorage length and bar diameter on the performance of the reinforced bond specially used in the tests are discussed. Testing results indicate that, under the condition the ratio l/d is given, the bond strength increases with mortar strength, and decreases with the increase of anchorage length/bar diameter. In view of the pull-out splitting strength of the mortar used and relative anchorage length, the least square method is used in combination with statistical regression to give a formula characterizing the bond strength.