Nanoporous silk fibroin (SF) films were prepared as SF film loaded with methoxy poly(ethylene glycol)-b-poly(D,L-lactide) (MPEG-b-PDLL) nanoparticles by film casting of MPEG-b-PDLL nanoparticle suspension-SF solution. Nanoporous structures of the SF films were formed due to self-condensation and nanophase separation of nanoparticles from SF film matrix during drying process. The films with SF/MPEG-b-PDLL ratios of 20/1, 20/2 and 20/3 (w/w) were prepared and investigated. The MPEG-b-PDLL nanoparticles can be observed on film surface and cross-section with 100-300 nm in size. The size of interconnected nanopore was in the range of 20 – 300 nm. The number and size of nanopores increased as increasing the MPEG-b-PDLL ratio. Thermal stability of the films studied from differential thermogravimetric (DTG) thermogram found that the nanoparticles dispersed into the SF films could improve thermal stability of each component. This indicated strong hydrogen bond interactions between SF and MPEG-b-PDLL were existed. Film transparency of the SF nanoporous films decreased when the MPEG-b-PDLL ratio was increased.