It was stated that infective larvae of root knot nematodes of kenaf distributed principally in 0-40 cm of soil layer.The number in the sandy loam was larger than that in the yellow loam and it is also true for the distribution depth.During the winter season,eggs and infective larvae cou-centrated mainly in the residue,and the number of over-wintering larvae in the inner rhizospherical soil was twice as in the outer rhizospherical soil.Four fluctuation peaks of larval number occured in the period of kenaf growth,and another appeared after harvesting.Through rotations of immuneor high-resistant crops with kenaf for one year,the populations of patho-genic nematodes was able to be reduced greatly.Control of the disease was discussed.