  In this paper, we revisit the weak gravitational lensing of CMB. The key
point is that the deflection angle of CMB photon varies with the redshift. From
this we obtain a set of modified power spectra. Compared with the ones
calculated before, the temperature, the polarization E mode and the cross power
spectra correction are of the order $0.01 %$, while the polarization B mode
correction is about $0.4 %$ (to $l=2000$).
