Abstract: Dosimetry parameters, including dose rate constant, radial dose function and anisotropy function, of model 81-02 ¹⁹⁸Au brachytherapy source were calculated in a 30 cm radius theoretical sphere by Monte-Carlo method for clinical application. For the single source, the deviation of dose rate constant is 1.113 cGy•h^－1•U^－1, and within 0.18% and 1.62% from the calculated and measured value (TLDs) of Dauffy et al. Calculated value of radial dose function, g(r),is in the rang of 0.1-10.0 cm at transverse axis. Anisotropy function, F(r,θ),is calculated in 0°-90° of θ with increment of 10° and 0.5-9.0 cm of r with increment of 1 cm. Empiric equations are acquired for radial dose function and anisotropy function by curve fitting.