Comparison of burnup characteristics of the High Temperature Engineering Test Reactor (HTTR) were conducted between experimental data and analytical results, and then applicability of a three dimensional whole core burnup calculation method to burned block-type HTGRs was studied. The calculations were performed by the SRAC/COREBN based on diffusion theory. We focused on changes in control rods (CRs) position with burnup as one of the HTTR burnup characteristics, and analyzed that in rated power with 30MW and zero power, respectively. In the HTTR experiments, different tendencies were observed in the changes in CRs position with burnup between rated and zero power. CRs position in rated power decreased with burnup, namely, insertion depth of CRs into a core increased with burnup. Meanwhile that in zero power was almost constant through burnup. In the analysis, similar results to the above were obtained. Thus, applicability of the three dimensional whole core burnup calculation method to burned block-type HTGRs was confirmed by experimental data.