To meet the energy demand of micro-type sensor and real-time condition monitoring system, and reduce the pollution of chemical batteries to water and soil, a piezoelectric airflow energy harvester based on resonant cavity was presented. In order to obtain the vibration state of the fluid in the energy harvester and the deformation characteristics of the piezoelectric transducer when the structure was different, the energy harvesters with different structures were established and simulated by COMSOL, the results showed that the structure of the generator had great influence on the deformation and vibration frequency of the piezoelectric transducer. The influential factors on the harvester properties were analyzed and proof experiments were carried out, the effects of excitation parameters (excitation distance and air pressure) and structural parameters (the length and diameter of the cavity and neck) on the output voltage were obtained. Under other given parameters, there were optimal excitation distance (d*f), length of cavity (l*c) and diameter of hole (d*r) for the voltage to achieve their peaks, besides, l*f/l*c/d*r and the corresponding maximum voltage were increased with the increase of air pressure. In addition, when air pressure was low, there was optimal length of neck to maximize the output voltage, l*r also was decreased with the increase of the air pressure and the corresponding maximum voltage was increased with the increase of the air pressure;on the contrary, when air pressure was high, the output voltage was the maximum without neck, and it was increased with the decrease of length of neck. As a result, the structure and scale of the cavity should be determined according to the air pressure. Under other given parameters, the optimum external resistance (R*) was increased with the increase of the length of neck (lr), and the output power (Pg) was decreased with the increase of the length of neck (lr), the maximum power of the energy harvester was 2.61mW in the process of experiment.