The present invention discloses a method for rapidly preparing samples with different water saturations, and belongs to the technical field of rock samples and concrete samples. The method comprises: 1) cutting a sample; 2) placing the cut sample into a baking oven to obtain a baked sample; 3) under a negative pressure constant-humidity environment, preparing a water saturation sample; and 4) according to the test scheme, sequentially preparing samples with different water saturations. According to the present invention, in the case of the negative pressure, the air in the sample pores is reduced, the penetration of the water vapor in the sample is accelerated, and the preparing time is shortened; the precision of the constant humidity device is controlled to precisely prepare the samples with different water saturations; and the operation is simple, the efficiency is high, and the high-precision and uniform-water distribution sample meeting the research requirements can be rapidly prepared.