the fig1 fig5 shows a schematic diagram of an alternative arrangement of the comprehensive two dimensional gas chromatography switching valve modulation system of the present invention this modulation system accomplishes modulation by two valve switching at the same time in a modulation period the detailed modulation process is explained exactly as that for the modulator valve system in fig1 however this modulation system reverses the switching between the valves in position x and y to accomplish the comprehensive two dimensional gas chromatography the difference between the fig5 design and the fig1 design is that in fig1 the valve connects the end of first column to the second column and in fig5 the valve connects the end of first column to the second column flow in fig1 design the connection to the end of the first column and the connection to the second column are in the same valve however in the fig5 design the connection to the end of the first column and the connection to the second column are in the different valve the modulation system can also be built on two valves with more than four ports however because of extra loops and ports involved it will not perform as simple and as good as four port valves the modulation system can also be built on one valve with at least twelve ports fig6 shows a schematic diagram.