Eccentricities of the mass center from the geometric center of two cylindrical source masses used in the HUST-99 measurement of the Newtonian gravitational constant G are determined by means of an electronic balance. Considering a linear density distribution of source masses as well as the effect of the air buoyancy, our value of G should be revised to be 6.6723(9)*10-11 m3 kg-1 s-2, which is 0.036% larger than our previous published value in Phys. Rev. D 59, 042001 (1999).