Abstract: The influencing factors of acoustic streaming in thermoacoustic waveguides with slowly varying cross-section are analyzed based on theoretical analysis and numerical simulation. The distribution curves of acoustic streaming velocity in waveguides with different characteristic scales are presented in several specific cases. The results show that appropriate forms of varying cross-section can strengthen or weaken acoustic streaming for specific acoustic fields and the thermophysical parameters have no effect on this part. In addition, the influence of time-average temperature distribution on acoustic streaming is substantial in tubes with a width of the order of the thermal penetration depth. Without time-average temperature distribution, the effect of heat conduction on acoustic streaming is great in tubes whose width is an order of about 10 to 20 times the viscous penetration depth.