As a new processing method for the production of modified starch, microwave heating was applied to native arrowroot starch. The effect of processing parameter on the sustained release properties of the obtained modified starches was investigated. The modified starch was blended with a model drug, theophylline, and then compressed into tablet using hydraulic press at a pressure of 19.6 kN for 30 s. The physical properties as well as drug release behavior of the compressed tablets were investigated. The results showed that the physical properties of different modified starches were about the same. The modified arrowroot starch displayed better sustained release properties than native starch. The modified arrowroot starch, which subjected to microwave heating using high level of water content, long heating time and high microwave power, demonstrated promising properties as hydrophilic matrix excipients for sustained release tablets.