To evaluate the pH value of mainstream cigarette smoke (MCS) in the simulated oral environment, with Cambridge filter to collect mainstream cigarette smoke particulate, oral solution by simulating shock to extract filter, pH composite electrode to determinate pH value of extraction solution, and set up a method to measure the pH of MCS. Correlation analysis was made between the pH and the contents of routine chemical components in MCS, between pH and the sensory evaluation of MCS. The results showed that: ① the pH value of MCS was highly correlated with the total particulate matter, tar, nicotine and H2O content of MCS, but not with the puffs of cigarette; ② the pH value of MCS was significantly correlated with sensation score of the smoke characteristics (smoke concentration, richness), taste style (sweetness, bitterness), comfort (irritation, convergence, residue/drying), but not strongly correlated with taste style-acidity of cigarette.