In the present paper non-spectral Interference of iron matrix whose concentration ranges from 0 to 5 mg·mL-1 has been studied by using ICP-AES.And its mechanisms are discussed through calculating every terms of the interference function and investigating the relation between the values of them and Fe matrix concentration.The results show that in a certain concentration range (0~5 mg·mL-1) Fe matrix has no significant influence upon excitation temperature and electronic number density.Most of the elements’ activity coefficient terms decreases with the increase of Fe matrix concentration.And the contribution of each term to the interference function is different according to atomic line and ionic line.It is the differencein ionization term between atomic line and ionic line that causes this.