The invention discloses a roadbed longitudinal crack treatment method based on a convex tenon type cement grouting geomembrane belt based, which comprises the following steps of: (1) drilling for coring: drilling a plurality of rows of drill holes on the side slope of a treated roadbed with longitudinal cracks by using a coring machine; (2) geomembrane belt arrangment: putting prefabricated geomembrane belts into the drill holes one by one, wherein the geomembrane belts are round pipe-shaped geomembrane belts made from geomembranes, the diameters of the geomembrane belts are the same as that of the drill holes, and the side walls of each geomembrane belt is provided with a plurality of rows of round through holes; and (3) injecting cement mortar under high pressure: injecting prefabricated cement mortar into the geomembrane belts through a high-pressure grouting machine. The invention has the advantages of reasonable design, simple steps, high construction speed, good treatment effectand low investment cost and can effectively solves the practical problems of larger investment, longer traffic closing time, greater influence on service functions of roads, poor treatment effect, and the like of the traditional roadbed longitudinal crack treatment method for areas with frozen earth for many years.