Biodegradation properties of chitosan-coated PGLA (poly (lactic-glycolic acid)) brachytherapy seeding carrier was investigated by continuous low-dose-rate irradiation of ,125,I seeds ,in vitro,. PBS (phosphate-buffered solution) was used to simulate internal environment ,in vitro,. Five ,125,I seeds with an apparent activity of 29.6MBq each were arranged in coated PGLA carrier. Weight loss, elasticity recovery rate and SEM (Scanning electron microscope) observation were used to evaluate its biodegradation properties. The coated PGLA carrier was slightly degraded by losing the weight of 10% and elasticity retention rate still kept at above 60% after two week’s exposure. The PGLA filament structure was well maintained and only a few coating layers were detached. With a maximum dose of 2.2kGy in the coated PGLA carrier after four weeks’ exposure to the ,125,I seeds, the weight loss rate was less than 50% and elasticity retention rate was 36%. SEM observation indicated further detachment of coating layers and fissure and slit of a few filaments. The results showed that continuous low-dose-rate irradiation delivered by the ,125,I seeds caused to some extent accelerated biodegradation of chitosan-coated PGLA after four weeks’ exposure ,in vitro, but majority of mass and certain elasticity were retained and the morphology structure was well maintained. The chitosan-coated PGLA carrier could maintain the space distribution of ,125,I seeds.