The work investigated the degradation behavior of cellulose acetate (CA) fibers in NaOH solutions in heterogeneous conditions and the effect of alkaline treatment on cellulase degradation of CA fibers. Weight analysis and IR spectra showed that the weight loss of CA fibers immersed in NaOH solution chiefly depended on acetylation. Alkaline treatment promoted the degradation of CA fibers in cellulase solution by reason of deacetylation, especially when the degree of substitution (DS) of CA fibers reached 0.8, cellulase degradation increased most markedly. SEM revealed a smooth surface except some thin holes in the CA fibers after immersion in NaOH solution with a lower concentration because of the formation of alkaline cellulose, and only in a higher concentration such as 5.0N, it could be observed that microfibers perpendicular to fiber axis distributed over the surfaces of the fibers. (NMR)-N-1 spectra suggested that only in a lower NaOH concentration (<= 0.25N), deacetylation reaction was affected by the reactivities of ester groups at position 2, 3, and 6 in anhydroglucose unit, but did not follow the theoretical trend in the three positions. Moreover, the DS for polymer molecules in CA fibers were dispersive after alkaline treatment in heterogeneous condition and the DS of the product increased during sequent cellulase degradation. This was also demonstrated by the result of IR analysis and Xray diffraction. (c) 2007 Wiley Periodicals, Inc.