The invention relates to an isolation method for crops, specifically to an isolation method for preventing mixing of different kinds of pseudo-ginseng. The method comprises: isolating different strains of pseudo-ginseng with isolating covers before pseudo-ginseng is bloomed, wherein the same strain of pseudo-ginseng is isolated with one isolating cover, completing the isolation one week before pseudo-ginseng is bloomed, and removing the isolating covers away 30 days after pollen dispersal of the pseudo-ginseng plants in the isolation area is completely finished. Each isolation cover includes supporting rods (1), an external net cover (2), and connection rods (3), wherein the supporting rods (1) and connection rods (3) form a frame, and the external net cover (2) is in fixed connection to the surface of the frame. The method can effectively prevent mixing of different kinds of pseudo-ginseng. The isolation is carried out via isolation covers. The method is simple to operate, and plantsdon't need to be transplanted, which is beneficial for growth of the plants.