The coronavirus disease 2019 (COVID-19) has spread widely around the world and has seriously affected the human health of tens of millions of people. In view of lacking anti-virus drugs target to SARS-CoV-2, there is an urgent need to develop effective new drugs. In this study, we reported our discovery of SARS-CoV-2 M(pro) inhibitors. We selected 15 natural compounds, including 7 flavonoids, 3 coumarins, 2 terpenoids, one henolic, one aldehyde and one steroid compound for molecular docking and enzymatic screening. Myricetin were identified to have potent inhibit activity with IC50 3.684 +/- 0.076 muM in the enzyme assay. The binding pose of Myricetin with SARS-CoV-2 M(pro) was identified using molecular docking method. In the binding pocket of SARS-CoV-2 M(pro), the chromone ring of Myricetin interacts with His41 through pi-pi stacking, and the 3'-, 4'- and 7-hydroxyl of Myricetin interact with Phe140, Glu166and Asp187 through hydrogen bonds. Significantly, our results showed that Myricetin has potent effect on bleomycin-induced pulmonary inflammation by inhibiting the infiltration of inflammatory cells and the secretion of inflammatory cytokines IL-6, IL-1alpha, TNF-alpha and IFN-gamma. Overall, Myricetin may be a potential drug for anti-virus and symptomatic treatment of COVID-19.