Paramagnetic salts perform satisfactorily in cryogenic refrigeration, and hydrated salt crystals are usually used as refrigerated materials at a rather low temperature. In this paper, a chromium potassium alum CrK(SO4)2·12H2O (CPA) single crystal with the size of 32 mm×32 mm×20 mm was grown by a slow cooling method. The relationship between the growth condition and crystal morphology was analyzed, and the thermal behavior, infrared spectrum, and magnetic performance of CPA crystal were also investigated. The results reveal that the CPA crystal exhibits a magnetocaloric effect up to 29.75 J·kg-1·K-1 in an applied magnetic field of 7 T at 2 K. A salt pill made by growing the CPA crystals on an array of copper wires in a sealed container was used in a two-stage single-shot adiabatic demagnetization refrigerator, obtaining a no-load temperature of 90 mK.