A comprehensive two-dimensional gas chromatograph, comprising a sample injector, a primary dimension column, a two-position three-way valve, a secondary dimension column, a three-way tube, a heating oven and a detector, wherein an inlet end(s) of the sample injector is connected to a carrier gas line and as well to a sample line, and an outlet end thereof is connected to a first end of the primary dimension column, a second end of the primary dimension column is connected to a first branch of the three-way tube, a second branch of the T-union is connected to a first end of the secondary dimension column, a second end of the secondary dimension column is connected to an inlet of the detector, a third branch of the three-way tube is connected to a gas inlet of the two-position three-way valve, and a first gas outlet of the two-position three-way valve is connected to the carrier gas line.