Abstract: Donghai Root-knot Nematode causes a new root-knot disease which damages sandy beach-growing citrus in large area along the coast of Fujian province.This paper described a serious decline of the infected citrus trees and reported three diseasedes phases and new root-knot symptom in the underground part.The three phases are.the infectious phase, the declining phasethe waning phase.The new root-knot symptom is,1.there are a lot of males in the root-knots besides females, they damage root system by jointly stimulating root tissue to induce giant cells at their juvenile stage:2.only males were found in the root-knots, they are able to induce giant cells and form smaller root-knots than the ones which induced by females.