The invention discloses a preparation method of a selenium-rich mulberry tea powder. The preparation method of the selenium-rich mulberry tea powder comprises the following steps: before tea harvesting time each year and after new shoots of tea leaves grow, spraying a selenium solution with a concentration of 100 mg/kg three times a day at the new shoots of the tea leaves until the day before harvesting; plucking the new shoots of the tea leaves, putting the new shoots of the tea leaves into sealing bags, uniformly mixing the new shoots with selenium yeast at a ratio of 1: 0.01, placing the obtained new shoots at a temperature of 25-27 DEG C for one day, and constantly rolling and baking the new shoots at a temperature of 60-68 DEG C for 30-40 minutes; after rolling and baking, treating the new shoots of the tea leaves under hot air at a temperature of 40-42 DEG C for 12-15 hours; after above hot air treatment, placing the new shoots of the tea leaves in a dryer, and conducting drying at a temperature of 120-128 DEG C until a moisture content is less than 5%; and then placing the obtain new shoots in a ball mill, maintaining the rotating speed of the ball mill at 400-500 r/min for 3-4 hours of ball milling time, and filling yarn bags with the obtained mulberry tea powder.