Abstract: In order to determine pH values of particulate matter(PM) and vapor phase matter of mainstream cigarette smoke(MS), the influences of the number of cigarette smoked, puff volume, concentration and volume of extraction or absorption solutions, time and frequency for oscillation extraction, acidity and basicity of blank extraction and absorption solutions on pH determination were studied.The results were as follows: 1) the proper conditions were puff volume 40 mL, cigarette number 15;extraction solution 50% isopropyl alcohol-water solution, extraction volume 80 mL, oscillation frequency 175 r/min, extraction time 30 minutes;and absorption solution 50% isopropyl alcohol-water solution, volume 100 mL;2) the relative standard deviation of the method was from 0.20% to 0.27%;3) the blank extraction solution and absorption solution presented alkaline, both of them affected the pH measurement of PM and vapor phase of MS.This method is suitable for the determination of pH values of PM and gas phase of MS.