Abstract: Finite element method is adopted for the numerical study of the correlation between ultrasonic emission characteristic and noseleaf shape of two types of horseshoe bat. With evolution and natural selection, most bats have developed an ultrasonic echolocation system with high performance, called biosonar, The signal sender is surrounded by complicated wrinkle noseleaf whose position and structure are considered able to change the direction of ultrasonic pulse. Experimental studies have suggested noseleaf really has complicated acoustic function. in this paper, the noseleaf samples of Bourret’s horseshoe bat and Rufous horseshoe bat are chosen to simulated. The first step is to acquire original biological data. In experiment, high-resolution X-ray micro CT machine is adopted to scan samples of noseleaf of two horseshoe bats to get original digital shadow images. Then the cross-section view of the noseleaves are reconstructed with the method of cone beam reconstruction. These images with 256 gray level are then processed through Gaussian filter and boolean process, and images with clear definition of air and biological tissue could be got. With three-dimensional digital image processing technique, three-dimensional digital image attributes oftwo horseshoe bat noseleaf are acquired. The near-field sound pressure distribution of the two noseleaves structure is simulated with finite element method, and the far-field sensitivity function is extrapolated based on Kirchhoff integral theorem from near field, to analyze the directivity at azimuth and elevation angles. Finally, the width of noseleaf ultrasonic beam in the direction of elevation angle is measured to get the ultrasonic emission characteristics of the two types of noseleaves. Thus, the correlation between the ultrasonic emission characteristics and the length of noseleaf sella of the two types of bats is gotten through contrast between the length of their noseleaf sella. The result indicates sella plays a significant role in controlling the directivity at elevation angle in the process of emitting ultrasound, and there is obvious negative correlation between the length of sella and ultrasonic frequency.