The diffusion doping of YBa2Cu3O7-x (YBaCuO) by gold causes a significant increase of the lattice parameter c by about 0.20%. This effect, resulted from a replacement of a copper ion by a gold ion, is used for examination of Au diffusion parameters in YBaCuO. It was shown that the diffusion coefficient of gold in the range 500-870 degrees C changed from 1 X 10(-11) to 6 X 10(-10) cm(2)/s with an activation energy of about 0.85 eV. For the gold-doped sample, the critical temperature increased by 3 K when compared with that of undoped YBaCuO. The critical current density increased from 50 A/cm(2) for the undoped sample to 280 A/cm(2) for the gold-doped YBaCuO. The possible reasons for the observed increases in T-c and J(c) due to gold diffusion in YBaCuO were discussed.