Salinity gradient cells are widely used in power generation from gradient concentration solutions of one electrolyte. High ionic flux sub-micro channels membrane can offer a high current density for salinity gradient power generation with a significant power output. Herein, based on numerical simulation model with Poisson-Nernst-Planck-Navier-Stokes (PNP-NS)equations, a high ionic flux sub-micro channel model with assumption is introduced that measured current is contributed by Cl−ionic flux across the membrane. An ion channel system is built for experiment, in which a glass membrane with regular symmetric sub-micro cylindrical channels and high effective channel area is applied, ion conductance and salinity gradient energy conversion property are tested. This PNP-NS equations model simulation fits experiment well, its mechanism is also studied by the model. In addition, by mixing artificial sea water (0.5 m NaCl) and river water (0.01 mm NaCl), the output power density of this 50-fold salinity gradient system can achieve4.16 W m−2, and the highest output power density will be up to 7.91 W m−2under a 0.5 m/0.001 m 500-fold salinity gradient. This high ionic flux membrane shows a good performance for practical application in salinity gradient power generation.