The Large High Altitude Air Shower Observatory (LHAASO) is built at an altitude of 4410 meters in Daocheng, Sichuan Province, China. As one of its major components, the Water Cherenkov Detector Array (WCDA) will focus on surveying the Northern sky for gamma-ray sources in a wide energy range. Because most of the triggered events are induced from hadronic cosmic-rays, suppressing a large number of background events is very important for LHAASO-WCDA. In this work, several sensitive parameters are chosen for the single parameter gamma/hadron discrimination based on topology characteristics of showers. Different methods of multivariate analysis are
also used in this study. Results from simulation data show that multivariate analysis can improve the separation significantly compared to single traditional methods. Some preliminary results using the separation technique on experimental data are introduced.