The semiconductor gas sensors sensitive to hydrogen and carbon monoxide are chosen to compose the gas sensor array, and an on-line data acquisition system is constructed, which is combined with the pattern recognition techniques of self organizing competitive network for the research of gas qualitative analysis. In order to eliminate the effect produced by the gas concentration, three kinds of normalization methods are developed to pre-process the sensors responses toward hydrogen and carbon monoxide. The research results show that the accurate identification of hydrogen and carbon monoxide in the finite range could be accomplished by relative method.