Abstract: Compared with the 1999 classification system of periodontal diseases, many changes have taken place in the new international classification of periodontal diseases and peri-implant diseases in 2018.The matrix based on stage and grade to appropriately define periodontitis in an individual patient was proposed which especially got the attention of the periodontists at home and abroad. This paper briefly introduces the background, content and clinical significance of this matrix based on stage and grade, and puts forward the application steps of it according to the national conditions of China.