In this paper,four calculating formulas (as follows) and some applied cases on n-fold calculating sieve formula are showed. ①It is used to calculate the number of prime number in the interval [1,a] (a is a natural number). ②It is used to calculate the number of different ways of 1+1 to an even integer. ③It is used to calculate the number of prime twins in the interval [1,a]. ④It is used to calculate the number of prime four folds in the interval [1,a].