Rat islets encapsulated in the immuno-isolated membrane were transplanted intraperitpneally into eleven streptozoto-cin induced diabetic mice. The effective rate was 91% while all were rejected in the non-encapsulated xenograft group. Four mice showed complete remission, and the longest normoglycemic period in those mice was 360 days. The pathological changes of islets in the long-term successful xenograft group were studied and atrophy was found. It proved that the immuno-isolated membrane can resist rejection during xenotransplantation.