The invention relates to a black tea fungus growing process, and in particular relates to a technology for making selenium-rich black tea. The technology comprises the following steps: carrying out pile fermentation on raw black tea material, steaming the tea, spraying eurotium cristatum conidial powder onto the tea, sealing the tea and then sterilizing, carrying out fungus growing process on the tea, carrying out ultrasonic treatment, etc. By adopting the ultrasonic treatment, the method can reduce the autolysis phenomenon of eurotium cristatum, and also has the function of fixing golden flowers, thus being beneficial to protecting organic selenium to the utmost extent, reducing the high-temperature oxidative degradation of the organic selenium, and preventing the thallus from being reduced by the golden flowers under the high-temperature condition. A great deal of eurotium cristatum conidial powder is adopted for quick fermentation, so that the growth of sundry fungus can be reduced, the problem of tea mildew can be avoided, and the influence of a culture medium in the eurotium cristatum liquid to the original flavor of the tea can be avoided.