The deep levels of the mid-wave infrared HgxCd1-xTe diodes(x=0.31), which are fabricated on Si substrates, are studied using the current-voltage-temperature (IVT) relationship. Firstly, the I-1/(kBT) relationship is fitted when the reverse current is dominated by generation-recombination process, and the deep level Eg/4 is calculated at the reverse bias 0.01 V. Secondly, the deep levels at different reverse biases are investigated. The origins of these deep levels correspond well to the reverse current mechanisms. Finally, the deep levels of different area diodes are calculated and compared. It is confirmed that the deep level is not related to diode area. This result is well corresponding to the theory, and indicates that the experimental method is correct.