Objective: To investigate the periodontal health status and associated factors of adolescents aged 12 to 15 years old in China. Methods: A cross-sectional national oral health survey was conducted in 2015-2016. The multi-stage stratified cluster sampling was used to select participants in all 31 provinces, autonomous regions and municipalities in the mainland of China. Each participant received a clinical assessment including periodontal bleeding and calculus, and 15-year-old adolescents received additional examinations including for periodontal pocket depth and attachment loss, using the latest criteria from the Oral Health Survey Basic Methods, as recommended by the World Health Organization (WHO). A self-answered structured questionnaire was designed to collect the data of background information and associated risk factors. Results: A total of 118,514 adolescents (14.0 ± 1.09 years old) completed all the oral examinations and the questionnaire. The prevalence of periodontal bleeding and calculus was 61.0% and 67.3% respectively. In the group of 15 year olds, 6.5% adolescents had periodontal pocket and 0.5% had attachment loss. Molars were often involved and, furthermore, calculus also occurred on lower incisors. The periodontal status of adolescents became worse as they grew up. The condition of girls was significantly better than boys. Conclusion: This survey illustrated a brief picture of periodontal status of adolescents in China showing that gingival bleeding and calculus were very common and frequent. Further actions on oral health education were necessary, especially for those in lower socio-economic classes. Keywords: adolescent, calculus, gingival bleeding, periodontal, the 4th National Oral Health Survey