We combine the recently proposed spherical harmonic expansion (SHE) method [Phys. Rev. X 2017, 7, 031003] with a modified network model to analyze the small angle neutron scattering (SANS) spectra from deformed entangled polymers. Focusing on the leading anisotropic component and the isotropic component in the SHE, the analysis gives a reliable value of the stretch ratio of the end-to end vector, and a reasonable estimation of the radius of gyration, of a single chain in polymers undergoing uniaxial deformation and relaxation. Moreover, it provides a practical way to evaluate the stress of deformed entangled polymers with the SANS spectra from a viewpoint of rubber elasticity.