Objective:To explore the method of computer discriminant on adenocarcinoma cells (ACC) and reactive mesothelial cells (RMC) amd establish the foundation on computer diagnosis for ACC in hydrothorax. Methods:Totally764 ACC of 44 cases and 709 RMC of 39 cases were collected from hydrothorax smears. Technique of computer image analysis was applied to test chromatics and morphological structure parameters of above cells. Approximately 80% cells were randomly selected as train group,and residual 20% cells as test group,the stepwise discriminant analysis was used in train group to establish the discriminant function,and the discriminant effects of function in test group were evaluated. Results:Stepwise discriminant showed that RP,BP,Rn,Bn,dmaj,c-dmin,c-An-Dn-Cn entered discriminant function,and its coincidence rate was 84.5%. The discriminant effect was significantly better than that in functions individually based on chromatics and morphological structure parameters(P < 0.05). Conclusion:The function combined with chromatics and morphological structure parameters has good discriminant effect,and it provides the analysis path of computer quantitative diagnosis for ACC in hydrothorax.