COVID-19, which originated in 2019, triggered a global pandemic in 2020. In the treatment of COVID-19, botanicals have achieved certain effects. My research found that the physiological mechanism of botanicals in the treatment of COVID-19 is that the alkaloids contained in plants can correct the PH value in blood and body fluids, maintain acid-base balance, and thereby inhibit the reproduction of COVID-19 and fungi. The pathological mechanism is that the invasion of COVID-19 will induce the proliferation of Candida albicans in the human body and cause acute leukemia. When Candida albicans proliferate in large numbers, it will destroy tissue cells, hinder the gas exchange in the blood, cause a large amount of carbon dioxide to stay, and cause the pH of body fluids and blood to be acidic. The alkaloids contained in plants can biochemically combine the hydrogen ions in body fluids and blood to reduce the concentration of hydrogen ions in body fluids and blood, thereby reaching acid-base balance and inhibiting the inflammatory response of Candida albicans.