The utility model discloses a gas chromatograph for analyzing total hydrocarbon components of gasoline and diesel oil catalytic cracking products. The gas chromatograph comprises a six-way valve, a twelve-way valve, three chromatographic columns, two quantitative tubes, two three-way stop valves and an FID (flame ionization detector). C1-C5 light hydrocarbon components and C6+ high-carbon hydrocarbon components in the gasoline and diesel oil catalytic cracking products are determined simultaneously and respectively with a valve-column switching technology. The gas chromatograph is applicable to research and the like on catalytic cracking reaction mechanisms by oil refineries and colleges and universities, convenient to operate, high in practicability, simple in structure and low in cost.