The present invention belongs to the pharmaceutical field, and provides the pharmaceutically acceptable salts of the compound (S)-7-(4-(l-(methylsulfonyl)piperidin-4-yl)phenyl)-N-(morpholin-2-ylmethyl)pyrido[3, 4-b]pyrazin-5-amine and the crystalline forms thereof, the solvates and the crystalline forms thereof, the pharmaceutical compositions comprising the same as well as the methods of preparing the same and the use thereof.