sing the method of diagonalization, in which zero-field wavefunctions from a kind of potential model are chosen as a basis, we caculate position and widths of avoided crossings points for highly exited Stark states of Li atom with principla quantum number n from 15 up to 22. We obtain the theoretical positions and widths in good agreement with values calculated by CA wavefunctions, and we present scaling laws of the field positions and widths of avoided crossing points that can be used to provide informati...