A novel ultra-fast micromixer of a quasi T-channel with electrically conductive sidewalls is presented here and some new phenomena in its mixing process are observed and reported. The mixing is about 10(2)-10(3) times faster than that by purely molecular diffusion, and about 10(2) times faster than that in existing micromixers, which are based on the electrokinetic instability (EKI). Both parallel and non-parallel channel are investigated and compared by evaluating their mixing. Mixing behaviors in the microchannels are studied in terms of scalar concentration distributions. It is found that with a small angle (about 5 degrees in this case) between the two electrodes sidewalls, mixing can be enhanced rapidly at even low AC voltage. The influence of the applied AC voltage phase shift between the two electrodes on the mixing process is also explored. The result reveals that the mixing is the strongest under a 180 degrees signal phase shift. Fast mixing is also achieved under high AC frequency in this micromixer. Fluorescent micro particles are used to visualize the flow pattern for better understanding of the mixing enhancement mechanism. The design of this micromixer could provide new opportunity for applications where fast mixing is demanded.