This paper is proceed from the history definition and effect of the root exudates, combing with the influence of plant species and the kinds of root exudates and quantity, which is considered that the carbohydrate and some poisonous matters of the root exudates supply the original microorganism in disease with nutrition and promote the propagate of the original microorganism in disease. Whose expression is the high incidence of a disease and the serious of the soil-spread disease.
