Disclosed is a crystalline form of an aminoalkyl tetracycline compound (4S,4AS,5AR,12AS)-4-7-Bis(dimethylamino)-9 { [(2,2-dimethylpropyl)amino]methyl} -3,10,12,12A-tetrahydroxy-1,11-dioxo-1,4,4A,5,5A,6,11,12A-octahydrotetracene-2-carboxamide (9-(2,2-dimethyl-propyl-aminomethyl)-minocycline) represented by the structural formula (1) shown herein. Also disclosed is a method for preparing the crystalline tosylate salt of said aminoalkyl tetracycline compound.