The genus Orius is a group of general predators and consumes a variety of pests including mites, thrips, aphids, eggs and young larvae of moths and other small, soft-bodied insects. It is an important biological control agent and plays an important role in controlling many pests. Researches on the effect of different preys on the predation and prey preference of Orius can provide basis for effective use of the agent in biological control. The predation and preference of newly hatched nymph, fifth instar nymph, female adult of O. similis to 3 species of preys, i.e., (Frankliniella occidentalis, Aphis craccivora, Tetranychus urticae and their combinations), were studied. The results showed that 1^st instar nymph of the predator, acclimated by feeding different preys, had no significant difference on predation capacity and preference to the prey. Comparison of C_i with null hypothesis showed that the preference of 1^st instar nymph of the predator to F. occidentalis was positive under 4 prey treatments with no preference to A. craccivora. There was no preference to T. urticae when feeding on T. urticae, while the preference to T. urticae was negative on other treatments. Fifth instar nymph of the predator, acclimated by feeding different preys, had a significant difference in predation capacity and preference to the prey, significantly increasing the predation to prior feed. For example, the preference to F. occidentalis was biggest with the value of 0.2580, when O. similis had experienced feeding on F. occidentalis. The predatory capacity and preference to A. craccivora was biggest when O. similis has experienced feeding on A. craccivora. The predatory capacity and preference to T. urticae significantly increased when feeding on T. urticae than those of feeding on other preys. Comparison of C_i with null hypothesis showed that the preference of 5^th instar nymph to F. occidentalis was positive under 4 prey treatments, and the preference to A. craccivora was positive when feeding on A. craccivora. The preference to T. urticae was negative except feeding on T. urticae. The predatory capacity of female adults to F. occidentalis was not significantly different when feeding on any prey. The predatory capacity to A. craccivora was bigger when feeding on A. craccivora and mixed preys than feeding on F. occidentalis and T. urticae. The predatory capacity to T. urticae was bigger when feeding on T. urticae and mixed preys than other treatments. The preference of female adults of O. similis was similar to 5^th instar nymph under different feeding treatments. The preference was strengthened when feeding on the pre-feed prey. The above results indicated that the predatory capacity and preference of 1^st instar nymph did not influenced by pre-fed. Prior feeding experiments had significant effects on the predation and preference of 5^th instar nymphs and female adults, so some learning behaviors may exist in O. similis.