  We measure the galaxy-ellipticity (GI) correlations for the Slogan Digital
Sky Survey DR12 LOWZ and CMASS samples with the shape measurements from the
DESI Legacy Imaging Surveys. We model the GI correlations in an N-body
simulation with our recent accurate stellar-halo mass relation from the
Photometric object Around Cosmic webs (PAC) method. The large data set and our
accurate modeling turns out an accurate measurement of the alignment angle
between central galaxies and their host halos. We find that the alignment of
central {\textit {elliptical}} galaxies with their host halos increases
monotonically with galaxy stellar mass or host halo mass, which can be well
described by a power law for the massive galaxies. We also find that central
elliptical galaxies are more aligned with their host halos in LOWZ than in
CMASS, which might indicate an evolution of galaxy-halo alignment, though
future studies are needed to verify this is not induced by the sample
selections. In contrast, central {\textit {disk}} galaxies are aligned with
their host halos about 10 times more weakly in the GI correlation. These
results have important implications for intrinsic alignment (IA) correction in
weak lensing studies, IA cosmology, and theory of massive galaxy formation.
