The present invention discloses a longitudinal guide for motor vehicle seats. The seats can be adjusted along the longitudinal direction and can be dissembled from the longitudinal guide. The longitudinal guide is provided with a bottom guide rail 22 and a seat guide rail 20 which can move relative to each other along the longitudinal direction. A positioning slot 24 is formed in the bottom guiderail. The seat guide rail comprises a base part 26 and a supporting part 28, wherein the base part comprises at least one front transverse bolt 32 and at least one rear transverse bolt 32; each transverse bolt is cooperated with the positioning slot 24; the base part can be adjusted between the lower position and the upper position relative to the supporting part; in the lower position, the transverse bolt 32 is not connected with the positioning slot 24, and the seat guide rails 20 can move relative to the bottom rail guide 22; in the upper position, the transverse bolt 32 is connected with the positioning slot 24.