Objective:To explore the effects of organic acids on tobacco pH and flue gas pH.Methods:34 kinds of single-grade tobacco and 11 kinds of finished cigarettes were taken as the research objects, and their non-volatile organic acids, tobacco pH, and the pH of mainstream smoke total particulate matter were measured respectively. Grey correlation analysis and principal component analysis were used to analyze the correlation between organic acids and pH.Results:The results of grey correlation analysis show that oxalic acid, palmitic acid, malic acid and oleic acid have a relatively large influence on the pH of single-grade tobacco; Palmitic acid, malic acid, linolenic acid and oxalic acid have a relatively large impact on the pH of cigarette cut tobacco; Malic acid, palmitic acid, linolenic acid and oxalic acid have relatively large effects on the pH of mainstream smoke total particulate matter of the cigarettes.Conclusion:Comprehensive analysis shows that malic acid and oxalic acid have a greater influence on the pH of single-grade tobacco, and malic acid and palmitic acid have a greater influence on the pH of cigarette cut tobacco and the pH of mainstream smoke total particulate matter.