The parasitoids in the genera of Encarsia and Eretmocerus are important biological control agents of whiteflies, and they not only parasitize the hosts but also feed and kill them. The feeding capacities of three whitefly parasitoids with different reproductive strategies (Encarsia sophia, Encarsia formosa and Eretmocerus melanoscustus) on their host, sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B, were determined on cabbage in a single instar no-choice experiment in the laboratory and a mixed-instar choice experiment in the greenhouse. Significant differences in host-feeding capacities were found in different whitefly parasitoids. En. sophia exhibited superior capacity of host feeding compared with En. formosa and Er. melanoscustus. Generally, En. sophia killed °Ö 3 fold more hosts than the other two parasitoid species. The percentage of whitefly nymphs killed by host feeding on total mortality caused by En. sophia was up to 59.7%, which was equivalent to that of parasitization. The three parasitoid species showed different preference of host feeding on different stage hosts. The parasitoids exhibited a clear preference to feeding older hosts than younger hosts. The significance of host feeding of En. sophia for biological control of B. tabaci is discussed.