The invention discloses a base constructing and freezing construction method for underground excavation of a subway station in a sandy cobble stratum. The sandy cobble stratum freezing construction method comprises the following steps that (1), underground excavation of a station vertical shaft, a horizontal channel and a first layer of the station for a subway is constructed; (2), freezing pipes are constructed according to the design requirement, the freezing pipes comprise the overall freezing pipes and the local freezing pipes, and the overall freezing pipes and the local freezing pipes form a freezing curtain of waterproof space; (3), after the freezing pipes are constructed, an active freezing stage is entered, and after the freezing pipes are constructed, a base plate of the second basement of the subway is poured; (4), when a closure of a freezing wall reaches the designed thickness, a vertical shaft and a horizontal channel of the third basement are constructed, the freezing pipes of the base plate are cut, base plates of the vertical shaft and the horizontal channel are poured of the third basement, and the rest freezing pipes of the curtain are cut; and (5), the freezing pipes of a main base plate in the station are cut, after soil masses of the third basement are all excavated, and when the overall base plates are poured to reach the designed strength, the rest freezing pipes are cut, and grouting and backfilling are conducted in the freezing pipes to strengthen the anti-overturning capacity of the base plates.