Acoustic streaming created by sharp-edged structures in micromixers can achieve a homogeneous and quick mixing. This study is performed numerically on the mixing performance of an acoustic sharp-edge-based micromixer using the convection–diffusion equation and the generalized Lagrangian mean theory. The perturbation theory is employed to solve the zeroth-, first-, and second-order equations. The impact of parameters such as displacement amplitude, background flow velocity, channel width, frequency, and sharp edge characteristics (height, angle, number, distance, asymmetry, and shape) on the mixing performance is evaluated to obtain the optimal model. It is demonstrated that the mixing performance is improved by increasing driving frequency, displacement amplitude, and sharp edge height. The mixing efficiency is enhanced by decreasing background flow velocity, tip angle, and channel width.