A similarity model is designed according to the type of bolts commonly used in coal mines and their grouted situation. To send out high frequency stress wave and meanwhile receive it on the top of bolt

an acceleration sensor with spring striking pin is invented. It is proved that the bolted length can be inspected accurately and the quality of a bolt can be evaluated by using the non-destructive inspection technique of high frequency stress wave. The rule to distinguish whether the quality of a kind of bolts is eligibility can also be found through express inspecting and drawing at random. It is confirmed by field tests that this method is economical and practical.