The fluids in microchannels get continuously stirred in the presence of vortex flow, which directly increases the interface area of the streams. Numerical analysis was done on a micromixer design that produces vortex flow with two inlet channels. At different Reynolds numbers, the mixing performance was examined for the microchannel with continuously decreasing cross-sectional area. The height of the intake channels of the vortex micro-T-mixer is half of the main mixing channel. Vortex flow is produced by the input channel's offset connection at one end to the main mixing channel (micromixer). Analysis has been done on fluid mixing and flow field for Reynolds numbers between 20 and 40. The vortex T-mixer's mixing efficiency is greater in small cross-sectional channels and rises noticeably as the Reynolds number rises. With tapered microchannel shape, the micromixers for microfluidic applications have the potential to increase mixing efficiency.