Early studies about territory defense of territorial male butterflies were focused on factors that may affect the outcome of contest. But rapid detection was so critical for territorial defense. The detection ability was correlated to visual system. Studies had focused on visual system such as the structure of eye optics and electrophysiology. However, it still existed one question about how do the owner detect intruder in the field. Some factors may affect the probability of detecting intruders from an owner, such as the distance, the size of the intruder, and background contrast. To determine what factor might affect detection ability of territorial male butterfly Hypolimnas bolina, two different sized butterfly models and four different luminance models were used to determine: 1. The reaction rate of the owner with differrent distances; 2. Test the detection ability at different relative position between intruders and owner (acute zone). 3. To test the visual angle hypothesis; 4. Test the luminance contrast effect. The results showed that the response rate decreased with distance but increased with model size. The owner had greater detection ability when the model was presented in the front rather than it on the side. Finally, the response rate was increased with model¡¦s low luminance. Besides, if the model was darker than its background, the owner¡¦s detection ability was greater. Previous studies indicated that a complex background may let the owner spend more time in detection. However, it was quite different with Hypolimnas bolina. In fact, the owner could quickly detect the model when the model was in a complex background, even there was without luminance contrast between the model and background.