The invention discloses a continuous on-line analysis device of benzene, total hydrocarbons, methane and CO in carbon dioxide, wherein a gas chromatograph is provided with two hydrogen flame detectors. The continuous on-line analysis device comprises a gas carrying pipe, a first six-way plane valve, a second six-way plane valve, a ten-way plane valve, a first chromatographic column, a second chromatographic column, a third chromatographic column, a fourth chromatographic column, a methanation transforming pipe and the gas chromatograph. The chromatographic columns with different characteristics are combined, one ten-way valve is used for completing sample introduction and back flushing operations, the methane and the carbon monoxide are separated from the carbon dioxide and enter into thenext chromatographic column, and simultaneously, the carbon dioxide is evacuated through back flushing without interfering the measurement of the methane and the carbon monoxide; the two six-way valves are used for respectively completing sample introduction and chromatographic column switching; and meanwhile, the benzene and the total hydrocarbons are measured. In the invention, the gas chromatograph in a laboratory can be used for realizing the functions of continuous on-line analysis, automatic sampling, sample introduction, sample back flushing, chromatographic column switching and the like. Meanwhile, the components of trace benzene, methane, carbon monoxide, total hydrocarbons and the like in the carbon dioxide can be analyzed on line.