The biodegradation behavior in vitro and in vivo of polycaprolactone poly (ethylene oxide) block copolymers (PCE) has been reported in detail. Photodegradation testof PCE was performed by exposure to UV light. The mechanical properties and the inherentviscosity of PCE samples which are subjected to photodegradation were determined . Thephotodegradation rate of PCE was much more faster than its hydrolysis rate and wasincreased with increasing poly (ethylene oxide) content. The experimental results also indicated that the pure poly (ethylene oxide)(PEO) can not be photodegraded alone. Amechanism for the photodegradation of PCE copolymers was proposed:the carbonyl groups in PCL segments catalyze the breakage of the PEO chains by a series of UV initiated free radical reactions. When the free radicals induce the degradation of PEO segments in PCE

the photodegradation of PCE mainly occurs in PEO segments.