Abstract: Finding a new solution for the acoustic and energy generation characteristics of the thermoacoustic piezoelectric energy harvester with general impedance boundaries is the core task of the paper. The thermoacoustic piezoelectric energy harvester includes a general impedance boundary, the hot buffer, stack, resonant tube, and energy harvester element. When the temperature difference on both sides of the stack reaches the critical temperature difference, the working fluid undergoes thermoacoustic coupling oscillation at the stack, causing deformation of the piezoelectric film and providing electrical energy for the external load. The modal distribution of the oscillation frequency, the real part of the acoustic pressure, and the imaginary part of the flow velocity are called the acoustic characteristics of the thermoacoustic piezoelectric energy harvester, while the equivalent quantized energy captured by the load is called the energy generation characteristic of the thermoacoustic piezoelectric energy harvester. Based on verifying the stability and reliability of the smooth Fourier series and Galerkin method, the paper applies this method to solve the acoustic characteristics and energy generation characteristics of the thermoacoustic piezoelectric energy harvester and explores the law of the effect of pipe length, external load, and boundary impedance on acoustic and energy generation characteristics. The studies show that the oscillation frequency of the thermoacoustic piezoelectric energy harvester is inversely proportional to the length of the tube. There is an impedance-matching relationship between the external load and the system, but excessive external loads will cause the system to lose its energy capture capability. Besides, the influences of pipe length and boundary impedance on the acoustic characteristics of the thermoacoustic piezoelectric energy harvester can be divided into high sensitivity, low sensitivity, and impedance failure zones, and an " acoustic characteristic identical impedance band " is found in the boundary impedance range. Hence the operating region can be chosen according to different demands and applications when designing the thermoacoustic piezoelectric energy harvester. The research achievements of the paper can provide a rapid prediction of the acoustic and energy generation characteristics of the thermoacoustic piezoelectric energy harvester and give a reference for regulating the acoustic and energy generation characteristics of the system by changing structural parameters or impedance boundaries and expanding the frequency band of piezoelectric energy collection.