The galactomannan from endosperm of G. sinensis seeds was used as sustained release material in the matrix tablets prepared at different concentration of 5, 10 and 15 % corresponding to formulations of G5, G10 and G15, for the release of theophylline. The drug release behaviors of the systems were investigated, including the swelling and morphological studies and texture analysis. The dissolution tests were conducted in 0.1 M hydrochloric acid and pH 6.8 phosphate buffered saline. The results of release studies demonstrated that G10 with 10 % galactomannan concentration showed a better control of the drug release profiles. The percents of cumulative drug released in 24 h were 98.8, 90.2 and 83.4 % for G5, G10 and G15, respectively. All the systems exhibited the typical morphological behavior of a swellable matrix. Results of texture analysis on the swollen tablets confirmed that diffusion drug release mechanism played the major role in G10 and G15 systems while the drug delivery kinetic towards an erosion/relaxation mechanism for G5 matrix tablets.