A new micromixer geometry is designed to efficiently mix operating microfluids by generating transverse rotation with helical streamlines. The micromixer consists of oblique grooves on the bottom and side of the channel with respect to the long axis of the channel. FLUENT software is used to visualize the mixing effect and to study the mixing efficiency when two completely separated species flow through the microchannel. The mixing effect of the new design is compared to the micromixers discussed in the literature. The simulated result demonstrates that the designed micromixer enhances the mixing effect and effectively removes the specific mixing dead zone in the microchannel.