  By adopting the differential age method, we utilize selected 17832 luminous
red galaxies (LRGs) from Sloan Digital Sky Survey Data Release Seven (SDSS DR7)
covering redshift $0<z<0.4$ to measure Hubble parameters. Using a full spectrum
fitting package UlySS, these spectra are reduced with single stellar population
(SSP) models and optimal age information of our selected sample are derived.
With the decreasing age-redshift relation, four new observational $H(z)$ data
(OHD) points are obtained, which are $H(z)=69.0\pm19.6$ km s$^{-1}$ Mpc$^{-1}$
at $z=0.07$, $H(z)=68.6\pm26.2$ km s$^{-1}$ Mpc$^{-1}$ at $z=0.12$,
$H(z)$=$72.9\pm29.6$ km s$^{-1}$ Mpc$^{-1}$ at $z=0.2$ and $H(z)$=$88.8\pm36.6$
km s$^{-1}$ Mpc$^{-1}$ at $z=0.28$, respectively. Combined with other 21
available OHD data points, a performance of constraint on both flat and
non-flat $\Lambda$CDM model is presented.
