For study of pharmaceutical properties of HPMCAS, film made by HPMCAS were tested for dissolution rate, for resistance in acidic solution and for stability under accelerated temperature and humidity condition. And also film coating preparations(VB₂ tablet, VB₂ granule, Cefalexin granule) were tested in vitro and in vivo test. The result is as follows. 1) pH-dependent solubility of HPMCAS was related with their dissociation constant. 2) HPMCAS is stable in accelerated condition and resist in acidic solution. 3) Sustained release part of preparation made by HPMCAS coating are as same pattern as organic solvent system of Eudragit L-90.