Abstract In some paramagnetic media, the effective field Hi which includes exchange interaction and external magnetic field, can cause the splitting of ground state energy level. In the region of the temprature T>Tc, the Curie temperature, there is certain probability distribution of electrons on two energy levels arised from ground state splitting. This induces the ground state energe level for double transition. It is proved by calculation according to this theory, there are several temperature characteristics for magneto-optical Faraday effect of the paramagnetic media. With the external magnetic field not too high, the ratio of the Verdet constant to magnetic susceptibility x is V/x = A(1+BT) in some media, or V/x = A(1 + B/T) in other media. It is also showed that both the real part θ′ and the imaginary part θ" of Faraday rotation are proportional to the effective field Hi, and with similar temperature character beyond the range of optical absorption.