The importance of replacing dialysis is growing day to day because of its disadvantages. Kidney-on-Chip is the right candidate to save kidney patients in an efficient way. The major parts of KOC are ultrafilter and bio-reactor unlike dialysis possessing of only ultrafiltration. This paper deals with designing of bioreactor for regenerating the reabsorption function based on size dependent selective function of kidney. The structure is designed with a main tubule carrying lumen fluid surrounded by blood tubules on the either side. The main tubule and blood tubules are connected through tiny transporting channels, which reabsorb the required solutes based on size. The flow velocity in the channels is found to be 8.82×10-5 m/s and total flow rate is 0.6 ×10-16 m3/s. Results show that the structure is capable of reabsorbing 52% of solutes. The present work has the potential to be applied in the design of Kidney-on-Chip. © 2019 IEEE.