Moisture-absorbent poly- (acrylate-co-methacrylate) was synthesized by solution polymerization, using N,N’-methylene bisacrylamide as the crossinglinking agent, sodium bisulfate and ammonium persulfate as the initiator. The moisture absorption properties of the copolymer in different temperatures and humidities have been systematically studied. Experimental results indicated that the moisture absorption behavior has been enhanced with the increase amount of methacrylate. Under different relative humidity, the moisture adsorption ability was distinct. When the relative moisture reached 40%, the humidity behavior became less evident. As the increase of moisture, the absorbency for moisture improves correspondingly. When the relative moisture get to 90%, the properties of this copolymer was obviously improved compared with the traditional materials, such as silica gel and molecular sieve.