Abstract：Based on the related test data of anchorage in rock and soil，the main factors affecting the bond strength between grouting anchor rod and rock or soil are analyzed；and the bond strength value is suggested. It is indicated that the distribution of the bond stress along the fixed length of the anchor rod is nonuniform when the anchor rod is loaded；and the nonuniform degree enhances with the increasing of the fixed length. The former formulae of calculating withdrawal resistance of the anchor rod are irrational for the value of the bond strength is kept constant for the anchor rods with different anchorage lengths. Therefore，the influence coefficient of the anchorage length on the bond strength should be introduced.
