A Trial of Shengmai Liquid for Long COVID Fatigue.

The goal of this clinical trial is to learn if Shengmai liquid works to treat Long Covid fatigue. It will also learn about the safety of Shengmai liquid. The main questions it aims to answer are: * Dose the Shengmai liquid will reduce the level of fatigue in the participants and reduce the fatigue scale score of the participants? * Dose the Shengmai liquid will reduce the level of anxiety and depression in the participants and improve the sleep quality and quality of life of the participants Researchers will compare Shengmai oral liquid to a placebo (a look-alike substance that contains no drug) to see if Shengmai liquid works to treat Long Covid fatigue. Participants will: * Take Shengmai liquid or a placebo every day for 8 weeks. * Visit the clinic once every 4 weeks for check up and test. There are a total of two telephone follow-ups, one follow-up 15 days after the treatment starts and another follow-up 30 days after the treatment ends. * Participants' medication responses and scale scores will be recorded.