A computation method of longitudes and latitudes of incident windows for the 60 laser beams on the spherical target charmber is reported. It is shown analytically that when the length ratio between the neighboring sides of hexagonal faces on the 32-face polyhedron inscribed in the chamber′s spherical faces equals 1.14～1.25, according to the criterion of irradiation uniformity on target for the “stretched soccer ball” model, the geometrical symmetry of the spatial arrangement of the beams comes to the optimum condition, and thus the irradiation uniformity of direct drive is improved.