Rockfall protection‐walls and ‐fences were constructed along the roadsides with steep cliff to ensure the safety of people’s lives and transportation networks. Generally, the walls were of gravity‐type made of plain concrete and the base of the steel posts of the fences were embedded into the box‐release space in the top of the walls. However, the anchoring depth of the posts has been designed by not considering dynamic effects due to rocks impacting but considering only static loads following the specifications of the design guideline. It may be important to establish a rational design method for the anchoring depth of the posts for upgrading those impact resistant capacity together with the energy absorption and capturing capacities of the fences against falling rocks. To accomplish this, static and drop‐weight impact loading tests of H‐section steel post embedded in the plain‐concrete block were conducted varying the anchoring depth of the post under the condition coupling between bending and shearing actions. The results obtained from this study were as follows:(1) the plastic hinge was formed in H‐section post near the base of foundation under not only static but also impact loading;(2) the concrete block failed in punching shear failure mode when the adequate anchoring depth of the post was not secured;(3) the adequate anchoring depth obtained from the impact load testing tends to be decreased comparing with that from the static load testing; and (4) the required anchoring depth obtained following the design specifications approximately corresponds to that obtained from the experiments.