Abstract: A method of burnup calulation is introduced in calculation of reactor physic in this paper. Burnup calculation is completed by interpolation table of macroscopic cross section vs burnup, interpolated method and solving diffusion equation. The calculated result compared with shearon Harri s's result is satisfied. The method has characteristic of use friendly, less calculated time and occuracy demand. Now it is used in the practical calculation of reactor physic. A effective tool is provided for engineering design.

Key words: burnup, interpolation, cross section