This paper established an interaction model of Aonidiella aurantii and its three parasitoids: Encarsia citrina, Aphytis melinus, Aphytis lingnanensis: H n+1 =λH n(sf 1f 2+tf 2f 3+uf 3) P n+1 =H ns(1-f 1) Q n+1 =H n(sf 1+t)(1-f 2) R n+1 =H n(u+tf 2)(1-f 3) f 1(P n)= exp (-aP n), f 2(Q n) =exp (-bQ n), f 3(R n)= exp (-cR n)The host is devided into 3 types according to scale area: s (above 0.55 mm 2), t (0.39～0.55 mm 2), u (below 0.39 mm 2...