Abstract: According to Specification for Geotechnical Investigation of Tall Buidings(JGJ 72-2004), the water level for prevention of up-floating should adopt the highest water level determined during investigation construction. But this specification doesn't suit the condition of multi-level grounduater.Therefore, the determination method of water level for prevention of up-floating under the condition of multi-level groundwater is discussed, and the condusion is:the water level for provention of up-floating under the condition of multi-level groundwater should adopt the highest water level of the stratum sat by foundation.