This paper proposed the quantitative relationship between electron affinity and induced effect. The relative computation shows that the relativity between electron affinity and induced effect is much better than that between electronegativity and induced effect. Its equation can predict the unmeasured values of electron affinity of substituting groups. According to these computated results, the correct experiment values of electron affinity can be chosen from the values of electron affinity which are measured by various experimental methods. The equation illustrates the effects of induced effect quantitatively and more accurately.