Disclosed is an energy-saving and eco-friendly filtration system which is capable of minimizing the amount of the energy required for the filtration, thereby remarkably reducing the cost of water treatment. The filtration system of the present invention comprises: a feed water tank for storing a feed water to be treated; a hollow fiber membrane module for filtering the feed water supplied from the feed water tank; and a filtrate tank for storing a filtrate produced by the hollow fiber membrane module, wherein the hollow fiber membrane module comprises a plurality of hollow fiber membranes for filtering the feed water, and the sum of head pressure of the feed water in the feed water tank and water pressure of the filtrate in accordance with siphon principle is higher than the threshold membrane pressure of the hollow fiber membranes.