We studied the prey preference of Wollastoniella rotunda to two prey species, Thrips palmi （second instar） and Tetranychus kanzawai （adult female）, under laboratory conditions. The presence of T. kanzawai did not affect the numbers of T. palmi consumed by W. rotunda. By contrast, the presence of T. palmi affected the numbers of the female of T. kanzawai consumed by W. rotunda. When either of two prey species was offered to W. rotunda, the number of T. kanzawai consumed by W. rotunda was higher than that of T. palmi consumed. When both prey species were offered at high density （60 T. palmi and 60 T. kanzawai）, the numbers of T. palmi consumed by the predator were higher than T. kanzawai consumed. However, when both prey species were offered at low density （30 T. palmi and 30 T. kanzawai）, numbers of T. palmi consumed by the predator were similar to T. kanzawai consumed. Based on these data, we argued the use of W. rotunda for the pest management of both species.