The current studies indicated that sound can improve the visual perception. However, whether the gain is influenced by temporal disparity between visual and auditory stimuli, and whether the gain is the same for older and younger adults remains unclear. To clarify this mechanism, ten older adults and 10 younger adults were invited to confirm and visual/auditory discrimination task. The visual target task, visual irrelevant task, auditory target task, and auditory irrelevant task randomly presented on the right or left hemi-space of the central fixation point and the subjects were instructed to respond to target stimuli rapidly and accurately. The results showed that in the younger adults, the gain was greatest in the simultaneous audiovisual condition. With the enlargement of temporal disparity between visual stimulus and auditory stimulus, the gain decreased significantly, and the alterative slope was different between auditory proceeded visual stimulus and visual proceeded auditory stimulus. In the older adults, the variation tendency was similar to younger adults, but in all conditions, the response of older adults was significantly slower than that of younger adults. Our results suggested that the visual gains were influenced by temporal disparity between auditory and visual stimuli, and further suggested that the gain mechanism between auditory proceeded visual stimuli and visual proceeded auditory stimuli was different, which indicated that the development of intelligent robot should consider the condition of the target subject to switch to the adapt procedure.