Abstract: This paper makes a study on the optimum plugging time,the optimum plugging site,the optimum plugging quantity and the optimum plugging process of secondary channel through the adoption of flow experiment of plane models.Study of optimum plugging time proves that the best time for plugging is when the water makes the breakthrough.Right after the coming into being of water channels,plugging is able to reduce the useless circulation of injected water and thus decrease the number of secondary channels.Study on optimum plugging site proves that the optimum site for plugging is the area near the water flooding well.The nearer the plugging site is to the water flooding well,the more effect on flow line,and higher sweep efficiency and oil recovery.Study on optimum plugging quantity proves that the more plugging agent used,the more complete plugging of high permeable formations,and thus higher sweep efficiency and oil recovery.With economic factors taken into account,the appropriate amount of plugging agent is about 15% of the pore volume of high permeable formations.Study on optimum plugging process testifies that multiple injection of plugging agent is better than the single injection.This law proves that multiple injection changes the direction of flow more obviously than single injection does,and thus improve the sweep efficiency,and ultimately greatly increase the oil recovery.