Abstract: The parasitism and development of Encarsia formosa (Gahan) on the tobacco whitefly, Bemisia tabaci Q biotype reared on plants of pepper, eggplant, tomato, poinsettia, and cotton were investigated at (26±1) ℃, relative humidity of 60%-80%, and the photoperiod of 16L﹕8D using the clip-cage method. Significantly higher parasitism rate was observed on pepper and eggplant (28.49% and 26.58%, respectively) than on tomato and poinsettia (17.62% and 16.36%, respectively), while parasitism rate was intermediate on cotton (21.25%). Parasitoid-induced mortality of whiteflies ranked from high to low: eggplant (40.41%), pepper (37.63%), cotton (33.82%), tomato (26.52%), and poinsettia (18.49%), which was consistent with patterns of parasitism rate. The wasp developmental duration on whitefly were significantly shorter when the hosts were on pepper (14.16 d) and tomato (14.53 d) than on other three host plants (more than 16.34 d). The wasp longevity on cotton and poinsettia (17.00 d and 9.60 d, respectively) were significantly longer than on the other three plants. No differences were observed in emergence rate of E. formosa among the tested 5 host plants. It is concluded that host plants could affect the biological characteristics of E. formosa on B. tabaci Q biotype, and the parasitism were high when B. tabaci Q biotype were fed on the pepper and eggplant.