Rhabditis sp.Bn strain was the first time found suppressive on plant parasitic nematodes(PPNs)in the rhizosphere of greenhouse cucumber.The nematode Bn was applied into soil at the rate of 1.0×1010 Juveniles/hm2 10 days before cucumber plants being planted in October 2004 and then once a month as treatment.The same volume of tap water was used as control.The density of PPNs increased sharply in control and reached 1 561 Js/100 mL soil in April,whereas it was less than 400 Js/100 mL soil in treatment,significantly lower than that of control(P<0.01).The densities of PPNs,Meloidogyne spp.and Tylenchorhynchus spp.were reduced by 70% and 87% respectively by applying Rhabditis sp.Bn strain.The root-knot index of cucumber in treatment was also reduced significantly(P<0.05)in April 2005.