In this paper, the quasi-ge'ostrophic Q-vector analysis -method is introduced. B/ means of Q-vector analysis, we diagnosed a severe cbnvective storm episode (4-5 Augest 1987) in Liaoning Province and compared the diagnostic result with LFM Prediction. The results suggest that the Q-vector analysis can reveal the synoptic and sub-synoptic scale circulation change during the severe convection and provide some valuable information for local short range weather forecasting.