Abstract: Burnup characteristics and worth deficit rules of control rod absorbers as nature hafnium, Ag-In-Cd alloy, pure silver and B₄C were profoundly investigated. The results show that the control rod worth of nature hafnium and pure silver decreases linearly with burnup, the control rod worth of Ag-In-Cd alloy and B₄C decreases non-linearly, the deficit of the control rod worth of B₄C is the largest at the same burnup, and the deficit of pure silver is minimum. The deficit rate of control rod worth for Ag-In-Cd declines rapidly at preliminary stage of burnup, and the deficit rate of other control rod worth increases with the burnup.