Blood capillaries are the ends of blood vessel tissues in human bodies, which are importantly functioned as exchanging the nutrients between bloods and interstitial fluids. Most blood capillaries such as in skins, skeletal muscles, cardiac muscles and lungs etc. have the walls with massively distributed cylindrical nanopores with diameters around from 50nm to 60nm. These pores are the only channels for transporting water, oxygen, carbon dioxide and ions, while preventing all the substances with the diameters greater than 60nm or a little more from passing through. The present paper presents the analytical results for the water permeability through these pores based on the nanoscale flow equation. The important results have been calculated like the pressure drop and the critical power loss on the whole pore channel for initiating the wall slippage and the volume flow rates through one single pore as function of the power loss on the pore channel.