The search rate for a target among distractors may vary dramatically depending on which stimulus plays the role of target and which that of distractors. In this experiment, we found that the time required to find a closed circle was significantly shorter than that of a circle with a gap.The results are completely the same as Triesman's research in 1985, which predicts that searching for a circle should be parallel and fast. We infer that it may due to the small quantity of subjects and the subjects' poor performance caused by the lack of strictness in manipulation of experiment.Generally speaking, there absolutely exists an asymmetry in visual search, and the reaction time is significantly effected by the display size in the search of feature.