The H2O megamaser technique provides a unique method to directly image the subparsec scale gas disks around the supermassive black hole(BH)at the center of active galaxies.These well-ordered Keplerian maser disks not only allow an accurate determination of Hubble constant by providing a standard ruler,they also allow measurements of BH masses to percentage level precision.These precise black masses are important for clarifying the nature of the M-sigma relation,especially at the low BH mass regime.In this talk,I will first give the latest update on the BH mass determination in the Megamaser Cosmology Project.I will show that the BHs in the megamaser galaxies do not obey the M-sigma relation defined by the elliptical galaxies in general and they usually show large intrinsic scatter.In addition,I will also show our latest discovery that the maser disks usually have a characteristic inner radius of 105 Schwarchild radii and discuss the possible physics behind.Finally,I will show the relative orientation between the maser disks and the circumnuclear disks < 500 pc and explore the implication for black hole accretion.