Abstract: The worth of control rod and its change along depletion are one of important features for reactor neutronics design. The control rods in pebble bed high-temperature gas-cooled reactor (HTR) were located in the hole of side graphite reflector. Its absorber was made up of annular B₄C, which had special depletion rules. The depletion characteristics in each absorber sub-zone and the changes of the control rod worth were analyzed, based on both the MCNP coupling another depletion module and the detailed modeling control rod absorber region. According to the analysis, the boron in inner region of absorber is depleted only a little, although most of boron in outer region of absorber is depleted, because of the strong space self-shielding effects in control rod-absorber. Therefore, the worth of control rod in the HTR decreases just a little at the end of reactor life time.