  The current discrepancy between the Hubble constant $H_0$ derived from the
local distance ladder and from the cosmic microwave background is one of the
most crucial issues in cosmology, as it possibly indicates unknown systematics
or new physics. Here we present a novel non-parametric method to estimate
Hubble constant as a function of redshift. We establish independent estimates
of the evolution of Hubble constant by diagonalizing the covariance matrix.
From type Ia supernovae and the observed Hubble parameter data, a decreasing
trend of Hubble constant with a significance of 5.6$\sigma$ confidence level is
found. At low redshift, its value is dramatically consistent with that measured
from the local distance ladder, and it drops to the value measured from the
cosmic microwave background at high redshift. Our results can relieve the
Hubble tension, and prefer the late-time solutions of it, especially the new
physics.
