The invention provides a method for screening a diterpenes natural product inhibitor from henry rabdosia leaves by taking the in-vitro inhibitory activity screening and crystal structures of main proteases of coronaviruses, such as SARS (Severe Acute Respiratory Syndrome), TGEV (Porcine Transmissible Gastroenteritis Virus), AIBV (Avian Infectious Bronchitis Virus), and the like, as a base. The compound with the following structural general formula can effectively inhibit the activity of the main proteases of the coronaviruses.