Constraining the Variation of G by Cosmic Microwave Background Anisotropies

We use the Cosmic Microwave Background Anisotropies (CMBA) power spectra to constrain the cosmological variation of gravitational constant G. It is found that the sensitivity of CMBA to the variation of G is enhanced when G is required to converge to its present value. The variations of G from the CMB decoupling epoch z ~ 1000 to the present time are modelled by a step function and a linear function of scale factor $a$ respectively, and the corresponding 95% confidence intervals for G/G_0 are [0.95, 1.05] and [0.89, 1.13], G_0 being the present value. The CMBA constraint is unique in the sense that it entails the range of redshift from z \approx 1000 to 0.