The invention relates to a method for determining void saturation of a large-void asphalt mixture in a seepage state. The method comprises the following steps: according to the volume and the voidage of a large-void asphalt mixture plate type sample, calculating void volume in the sample, weighing the dry mass of the sample, then performing a seepage test, and taking the minimum water head height of runoff appearing on a runoff surface of the sample as a water head of the sample in a seepage state; then under the water head, seeping water on the plate type sample, after seepage is started for 10min, quickly removing a water storage tank of a seepage meter, collecting permeating water in a period from this moment to a moment when water does not permeate from a permeation surface of the sample, and calculating a dry-wet mass difference value of the plate type sample before and after seepage, thus determining the volume of the water in the voids of the mixture in the seepage state; finally taking a ratio of the volume of the water in the plate type sample to the void volume in the sample as the void saturation of the large-void asphalt mixture in the seepage state. The method is simple, and the water retaining property of the large-void asphalt mixture plate type sample is visually reflected.