Abstract: The fine-structure parameters are calculated by a semiempirical method for six 1sng configurations of a helium atom using new refined energy values. After diagonalization of second-rank energy-operator matrices (levels ³ G ₄ and ¹ G ₄ ), the discrepancies between the calculated and experimental energy values are virtually equal to zero. The main concern was with the study of the Zeeman structure in order to determine the gyromagnetic ratios for all four levels of configurations. This is topical because analogous experimental data are absent for the studied configurations. The gyromagnetic ratios can be calculated only in the linear region. This region has been established for all the considered configurations. The specific features of Zeeman splitting—crossings and anticrossings of magnetic sublevels—were also studied. The data obtained can serve as a guide for further experimental studies.