Abstract: According to the phenomena of the anchoring slippage and other unreliable anchoring occurred in the anchoring device of the anchor in underground mi ne, in order to get the slippage causes of the anchoring device and to improve the anchoring relibility of the anchor, the dynamics analysis, lab analysis method and ot her methods were applied to get the main factors of the anchor device slippage and the major materials of the anchors applied to the coal mine were preliminarily invest igated. The analysis results showed that hardness difference between the anchor and shim irrational, diameter error of the anchor too high, strength and hardness of th e anchor too high, critical distance irrational and anchoring device quality poor would be main factors to influence the reliability of the anchoring. Therefore, an effective reference index to reduce the slippage probability and to improve the reliability of the anchor should have hardness difference between the anchor and shim over HRC1 0, the anchor diameter error should not be over +0. 400. 20 mm, the actual strength of the anchor should be lower than the tensile strength and aspace limited distance should be a shim exposed distance plus a retuned distance of the anchoring device.