NOVELTY - The system has an ejector (100) mounted to a hydrogen purge line (18) extending from a purge valve (16) to introduce air from outside. A post-treatment system i.e. humidifier, is connected to an exhaust line (28) of the ejector to remove hydrogen discharged from the exhaust line. The treatment system supplies humidified air to an air electrode (20) of a fuel cell stack (10), and the exhaust line of the ejector is connected to the inside of the humidifier. A catalyst combustion device i.e. flame combustion device, is mounted to the exhaust line of the ejector.    USE - Hydrogen discharge system for a fuel cell system for generating electricity in a fuel cell vehicle e.g. motor vehicle such as passenger automobile e.g. sports utility vehicle (SUV), bus and truck, watercraft e.g. boat and ship, and aircraft.    ADVANTAGE - The system ensures safety of the vehicle by optimizing dilution of hydrogen discharged from the fuel cell, and ensures silent operation of the vehicle by reducing noise generated during discharge. The hydrogen exhaust line is connected to the inside of the humidifier such that the water contained in the exhaust hydrogen is introduced into the humidifier, thus efficiently humidifying the air supplied to air electrode. The ejector is connected to the hydrogen purge line, and the post-treatment system is provided at an outlet port of the ejector so as to remove a considerable amount of hydrogen easily, while improving humidification of the fuel cell stack, thus improving the performance and durability of the fuel cell stack. The system easily controls the amount of air supply based on the selection of ejectors, and avoids separate control logic. The system easily prevents excessive rise of temperature by controlling the amount of outside air.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a hydrogen discharge system for a fuel cell system.    Fuel cell stack (10)    Purge valve (16)    Hydrogen purge line (18)    Air electrode (20)    Exhaust line (28)    Ejector (100)