Abstract: Biochemical detection and analysis plays an important role in many fields, and many of the target substances are in low concentrations. Microfluidic detection platform has been developed for its low cost and rapid detection. Microfluidic enrichment is important to improve the sensitivity of microfluidic detection system. This paper studied the enrichment of fluorescent ions and cortisol aptamers using a double-T-shape channel, which could achieve the function of sample driving by electrokinetics. It is found that the structure has different enrichment effect and different enrichment area for different sizes of substances. For those substances with larger size relative to ions, it can be concentrated in a short time under low voltages, and the enrichment region is far away from the microelectrode, which is of benefit to both the sample and the electrode. By using this new enrichment effect, we achieved the detection of cortisol with the concentration of 0.1 μg/mL.