Lycium　barbarum　polysaccharide　(LBP)　was　subjected　to　ultrasonic　degradation　under　the　controlled　conditions,　such　as,　temperature,　irradiation　time,　initial　pH　value,　and　concentration　of　solution.　The　ultrasonic　degradation　of　LBP　was　demonstrated　by　the　changes　of　intrinsic　viscosity.　Viscometry　was　used　to　study　the　degradation　behavior　and　a　kinetic　model　was　developed　to　estimate　the　degradation　rate.　The　results　showed　that　the　degradation　rate　was　reduced　with　the　increase　of　solution　concentration　and　pH,　and　increased　with　increase　of　temperature.　The　relationship　between　the　number　average　molar　mass　(M-n)　and　intrinsic　viscosities　as　interpreted　using　the　Mark-Houwink　equation　suggested　that　LBP　adopted　a　flexible　coil　conformation　in　aqueous　solution.　The　activation　energy　of　ultrasonic　degradation　of　LBP　is　26.5　kJ/mol,　which　indicates　that　the　ultrasonic　degradation　is　a　convenient,　time　saving,　and　cost-efficient　method　for　obtaining　a　desired　molecular　weight.　(C)　2010　Wiley　Periodicals,　Inc.　J　Polym　Sci　Part　B:　Polym　Phys　48:　509-513,　2010