In order to improve the ability of acoustic emission modal recognition of Micro/nono Cupling Fiber Sensor (MCFS), based on the theory of modal acoustic emission, the influences of the effective sensing area structure, length and symmetry of micro/nono coupling fiber on the modal identification ability of the sensor has been studied in experiment, and the orientation properties of the optimized sensor have been analyzed. Experiment results show that: When the effective sensing area structure is “X” type, including separation zone, exact taper zone and waist zone, the sensor can`t identify the S0 modal and the integrity of the identified A0 modal is poor; when the effective sensing area structure is “” type, including waist zone and all the exact taper zones, the sensor can identify the A0 modal and identify S0 modal completely. When the effective sensing area is symmetric, the integrity of the measured signal is good; when the effective sensing area is asymmetric, the integrity of the measured signal is poor. For the“X” type structure, in the separation zone partial sound wave energy is attenuated, the sensitivity of the sensor increases as the length of the effective sensing area decreases; however, for the “”type structure, the sensitivity of the sensor decreases as the length of the exact taper zone decreases due to the strain magnification effect of the exact taper. The modal identification ability of the sensor decreases as the detecting angle decreases, the effective detecting angle range is from 45° to 135°. This study has great significance to the application of this sensor in modal acoustic emission.