Abstract: A low-fuel consumption and low-pollution combustion system supplies an engine with a mixture, in which oxygen contained in air is separated from nitrogen through a PSA (pressure swing adsorption) whereby oxygen having purity above 95% and a fuel mixture is fed into and burned in the combustion chamber obtaining a desired engine output with low-fuel consumption. Nitrogen is previously removed so that nitride oxide can be minimized during combustion procedure and CO and toxic gas derived from incomplete combustion can be minimized. The system obtains high engine output and low-fuel consumption by reducing toxic gas derived from incomplete combustion. The system includes an oxygen separator for separating oxygen from nitrogen by introducing external air into adsorption towers with predetermined pressure while storing the oxygen separated from the nitrogen in an oxygen storage tank and exhausting the nitrogen.