The effect of electric field applied along [111] on EPR spectra of SrCl2:Co++ has been investigated. The result shows that electric field causes the crystal lattice to distort and deviate from its original cubic Oh symmetry to C3v symmetry. We have successfully explained the experimental rule that zero field splitting parameter D depends linearly upon electric field strength E and also predicted the coefficients of the change of the structure parameters a = - 8×10-5 a0 mm/kV (parallel to the electric field), β= 1.66×10-4 a0 mm/kV (perpendicular to the electric field).