Abstract: In order to study the spent fuel dense storage feasibility of a new type of fuel assembly with 4.95% enrichment,taking the spent fuel storage pool of Ling’ao Nuclear Power Station Units 3 ＆ 4 as calculation model,and using the burnup-credit analysis sequence STARBUCS in SCALE5.1 code system,this paper analyzes the yield changes of actinium nuclides and fission products in different burnup conditions as well as its effect on reactivity.Also,based on full burnup credit level,this paper shows the calculation for the critical security of the pool in different burnup levels and storage periods,and also shows the loading curve for spent fuel storage pool region II.The calculation result indicates that this new type of fuel assembly can be densely stored in the spent fuel storage pool region II when its burnup can reach 45GWd.t^-1（U）.