We derive constraint on the effective number of neutrino species N _ { \nu } from the cosmic microwave background power spectrum of the WMAP and galaxy clustering power spectrum of the SDSS luminous red galaxies ( LRGs ) .
Using these two latest data sets of CMB and galaxy clustering alone , we obtain the limit 0.9 < N _ { \nu } < 8.2 ( 95 % C.L . )
for the power-law \Lambda CDM flat universe , with no external prior .
The lower limit corresponds to the lower bound on the reheating temperature of the universe T _ { R } > 2 MeV .