  We investigate the cosmic evolution of the ratio between black hole mass
(MBH) and host galaxy total stellar mass (Mstellar) out to z~2.5 for a sample
of 100 X-ray-selected moderate-luminosity, broad-line active galactic nuclei
(AGNs) in the Chandra-COSMOS Legacy Survey. By taking advantage of the deep
multi-wavelength photometry and spectroscopy in the COSMOS field, we measure in
a uniform way the galaxy total stellar mass using a SED decomposition technique
and the black hole mass based on broad emission line measurements and
single-epoch virial estimates. Our sample of AGN host galaxies has total
stellar masses of 10^10-12Msun, and black hole masses of 10^7.0-9.5Msun.
Combining our sample with the relatively bright AGN samples from the
literature, we find no significant evolution of the MBH-Mstellar relation with
black hole-to-host total stellar mass ratio of MBH/Mstellar~0.3% at all
redshifts probed. We conclude that the average black hole-to-host stellar mass
ratio appears to be consistent with the local value within the uncertainties,
suggesting a lack of evolution of the MBH-Mstellar relation up to z~2.5.
