Abstract: In order to verify the validity of dichotomy method to convert CT numbers into chemical composition of tissues， the E-μ_ρ function model is constructed according to the principles of the interactions between γray and matter. Based on the E-μ_ρ function model， the coefficients of E-μ_ρ function of human body’s major elements and tissues were obtained with the regression analysis， and the availability of dichotomy method was testified through the medium of two factors， the coefficients of E-μ_ρ function of human body’s tissues and the mass percentage of component tissues. The result shows that the fitted value is reasonable and the maximum error is lower than 10%. So it can be proved that the dichotomy method is an effective way to deduce elemental mass of tissues through CT numbers.