Abstract: An adjustment method of moisture content and dense state for a hydrogel improved subgrade based on weather-resistance during an in-service period, including: step 1: carrying out surface cleaning and compaction of ground; step 2: preparing hydrogel improved subgrade raw material; step 3: paving the prepared material on the surface to form first-layer improved subgrade; and step 4: paving plain soil subgrade onto the first-layer. The method combines the water absorption and release function of the modified resin and the characteristic of the gel state thereof, to pave the improved subgrade in layers, which can absorb water and slightly expand when the water content in the subgrade is increased to a certain threshold value, and a strength and compactness protective layer can also be formed at the connection sections of the ground and the subgrade, and the subgrade and the pavement, to prevent the pot-cover effect from occurring.