  We make the in-orbit calibration to the point-spread functions (PSFs) of the
collimators of the Hard X-ray Modulation Telescope with the scanning
observation of the Crab. We construct the empirical adjustments to the
theoretically calculated geometrical PSFs. The adjustments contain two parts: a
rotating matrix to adjust the directional deviation of the collimators and a
paraboloidal function to correct the inhomogeneity of the real PSFs. The
parameters of the adjusting matrices and paraboloidal functions are determined
by fitting the scanning data with lower scanning speed and smaller intervals
during the calibration observations. After the PSF calibration, the systematic
errors in source localization in the Galactic plane scanning survey are 0.010
deg, 0.015 deg, 0.113 deg for the Low-Energy Telescope (LE), the Medium-Energy
telescope (ME) and the High-Energy telescope (HE), respectively; meanwhile, the
systematic errors in source flux estimation are 1.8%, 1.6%, 2.7% for LE, ME and
HE, respectively.
