Cs atoms have large hyperfine Zeeman separations in a high magnetic field. Cs vopor is optically pumped and detected with diode lasers in the high magnetic field. We obtained the steady absorption spectra and used them to investigate the steady population distribution, relaxation transitions, and electronic spin polarizations at different frequency tunings of the pumping laser. It is show that the collision-induced modificatin of hyperfine Zeeman interaction has taken part in the process of relaxation and polarization. We also introduced a new method for measurement of electronic spin polarization of alkali atoms in high magnetic fields.