Abstract: In view of problems of high cost and big volume of petroleum gas measuring system by use of imported equipment, the paper proposed a design scheme of measuring system of wellhead gas components of petroleum drilling. The system uses catalytic combustion type gas sensing probe and takes wheatstone bridge as measuring unit. When gas sensing probe meets measured gas, resistances of wheatstone bridge would change with changing of temperature if the gas could be ignited by electrode, so as to obtain gas concentration. Results of measured gas concentration are displayed, stored and generated report automatically through upper computer LabVIEW program. The actual application showed that the system has low cost, convenient operation and sensitive response, whose measured results are synchronous with imported equipment.