Biodrgradable polymer was prepared as thermoplastic starch. Due to poor mechanical properties and high water absorption of TPS, thermoplastic rice starch (TPRS) was modified by reinforcing with natural silk protein fiber, as an alternative choice of fiber reinforcement. Different contents and lengths of silk fiber were varied and used as the reinforcement. Internal mixer and compression molding machine were used to mix and shaped the TPRS/silk composites. It was found that stress at maximum load and young’s modulus of the TPRS/silk composites significantly increased with the incorporation of silk fibers. Water absorption of the TPRS/silk composites was also dropped by the addition of silk fiber. Moreover, thermal degradation temperatures of the TPRS/silk composites shifted to higher temperatures by the inclusion of the silk fiber. Functional group analysis and X-ray diffraction patterns were analyzed by FI-IR and XRD techniques, respectively. Furthermore, color measurement, morphology and biodegradation by soil burial tat were carried out for different TPRS/silk composites.