The influence of hydrogen on the electronic structure of an intermetallic compound has been studied from magnetization measurements in ultrahigh magnetic fields up to 130 T for a prototype system YCo3Hx. The dependence of the magnetic moment on hydrogen content and magnetic field lead to the following conclusions. The general structure of the density of states (DOS) in the upper part of the 3d band is still maintained in the hydride, but the curvature of the DOS curve is slightly modified in the β phase x = 1.0-1.9), and more strongly modified in the γ phase (x = 3.2-4.0). The modification of the DOS is related to the occupation sites of hydrogen. The electronic population in the 3d band is hardly changed upon hydrogenation, and it is about +0.1 electron Co-1 per absorbed hydrogen atom. The electrons originating from hydrogen atoms are almost contained in the metal-hydrogen bonding band. The rest of them occupy the 3d band, causing the Fermi level to shift slightly upwards.