Nonlinear vocal phenomena is a ubiquitous feature of animal vocalizations, accounts to its evolutional significances received considerable recent interest. Nonlinear phenomena generally emitted when animals are under aggressive circumstance and maybe have specific function. However, the studies of bats" nonlinear phenomena are mostly descriptive, very little is show their function. Myotis pilosus"s aggressive calls contain two kinds of syllable, sAFM and ND-sDFM, which can constitute three types of calls: only contain sAFM syllables (A), only contain NB-sDFM syllables (B), and contain both sAFM and NB-sDFM syllables (C). A type doesn"t contain nonlinear phenomena, B type contains nonlinear phenomena, and C type is a transitional type from A to B. In this paper, the three types of calls were played back to the bats, and then record bats" 7 kind behavior response (head up, leg movement, ear movement, echolocation, thriller, crawling, mouth open), the results of leg movement and echolocation numbers suggest that to the different calls, the bats" response are different, what"s more, the response intensity to the call type which contains nonlinear phenomena is higher. We argue that these findings support the unpredictability hypothesis and show that nonlinear vocal phenomena may have adaptive function.