Jahn-Teller effect of spectrum structure and g factor of electron paramagnetic resonance in ZnSiF66H2O∶Fe2+ are explored. The crystal structure of ZnSiF66H2O found by the single crystal neutron diffraction method may be described with two ions SiF6- and Zn(H2O)++. Zn(H2O)++∶Fe2+ of locally trigonal (C3v) symmetry expresses the main spectral propectry of the crystal. The crystal-field and spin-orbit interaction Hamiltonian matrixes and the formula of electron paramagnetic resonance have been composed by the irreducible representation method. The zero-field splitting parameters (D, F-a) and g factor of the electron paramagnetic resonance of Fe2+ ions in ZnSiF66H2O∶Fe2+ crystal are presented by the crystal-field and spin-orbit interaction Hamiltonian matrixes. The contribution of low-spin state 3L to zero-field splitting parameters is studied to be important and strong, whereas the contribution of g factor is ignorable. The structure of crystal is calculated which proves the existance of Jahn-Teller effect. The calculated results are in good agreement with the experimental data.