The Villermaux-Dushman fast parallel competing reaction was used to determine quantitatively the micro-mixing performance in the T-shaped micromixer with 600 μm width and 300 μm depth. The flow was almost ideal plug flow in the Reynolds number range 55—1600 and its corresponding Péclet number ranged from 7.0×106 to 2.0×108.The effects of inlet and outlet scale

micro-channel length

volumetric flow ratio on the micro-mixing performance were studied in detail.The micro-mixing performance was expressed with segregation index

Xs.The smaller the Xs

the better the micro-mixing.The experimental results showed that Xs increased with increasing volumetric flow ratio at the same Re.There existed a critical Rec under the condition of different inlet and outlet geometric structures.Xs decreased with increasing Re when Re<Rec

while Xs reached about 2.7×10-4 and remained constant when Re>Rec

indicating that almost perfect mixing in the T-sharped micro-mixer was achieved.