In situ Raman spectroscopy has been used to investigate uniaxial stretching of polyethylene (PE) gels with various PE contents. Molecular orientation of the crystalline chains proceeds beyond the yield point and higher orientation is attained for PE gels with higher PE content, but orientation perpendicular to the stretching direction persists up to the highly stretched region. This biaxial orientation is essentially the same irrespective of the PE content, and it can be explained by the inhomogeneity embedded in the PE gel. The PE content dependence of the second-rank orientation parameter < P-2 > at high strain is similar to that of the dynamical mechanical properties, suggesting that the deformation mechanism is consistent during the entire stretching process from the elastic region to the highly stretched region.