The DFT calculations were used to investigate the electronic structure of CdIn2Te4 and the electronic filed gradient (EFG) of the defects in this compound.The calculated band gap of CdIn2Te4 was quite consistent to the experimental value and it was predicted to reach the maximum,～1.23 eV,when Te around at the position (0.25,0.25,0.125).The interaction between In 5s and Te 5px,5py sensitively varied with the Te position was found to be the cause for the band gap variation.