Provided is a multifunction selection valve for use in a liquid chromatography system. The multifunction selection valve includes multiple ports to which both ends of a 1st dimension separation column may be connected at a part thereof, the multifunction selection valve including: a fluid passing mode in which a fluid introduced thereto is not passed through the 1st dimension separation column but is discharged; a column passing mode in which the fluid introduced thereto is passed through the 1st dimension separation column and then discharged; and a fluid blocking mode in which the fluid is prevented from being introduced. When using the multifunction selection valve, it modifies the flow paths of chromatographic solvents so that the resultant multifunctional liquid chromatography system allows one-dimensional separation, two-dimensional separation, on-line digestion and on-line phosphopeptide enrichment by a single binary pump.