Abstract: The silk fibroin fibers buried in soil for several months were measured and analyzed in surface shape,crystal structure,molecular conformation and mechanical properties,and compared with polyester fibers.The results revealed that there were some delves in the surface of silk fibroin fibers buried in soil for above two months,and the numbers and sizes of delves increased with burial time.After being buried in soil for 6 months,the strength and strain at break of silk fibers decreased to about 10% of a control sample′s,and the fibers were completely degraded when burial time was 9 months.The crystallinity of biodegraded silk in soil was almost unchanged,however,the molecules tended to beαhelix and random coil structures.