Abstract: A code for calculating the depletion sensitivity coefficient of atomic densities is developed on the basis of a first-order generalized perturbation theory. The sensitivity coefficient of atomic density of 244 Cm at 50GWd/T due to the change of cross section is analyzed, and the results show that the sensitivities to the fission cross section of 235 U and 239 Pu and the capture cross section of 238 U, 240 Pu, 241 Pu, 242 Pu and 243 Am are large; the energy dependent sensitivity of 244 Cm to the capture of 243 Am in thermal and resonance regions is much larger than that in the fast region, therefore, the accuracy improvement in the thermal and resonance regions should take a higher-priority than that in the fast region.