A novel injectable thermosensitive hydrogel system composed of N-trimethyl chitosan chloride (TMC) and beta-glycerophosphate (beta-GP), coded as TMC/beta-GP, was designed. The morphology and rheological behavior of hydrogels were characterized by scanning electron microscopy and rheometer, respectively. Their swelling properties were carefully studied. The results revealed that the TMC/beta-GP system was liquid with low viscosity at low temperature, which allowed it to be an ideal injectable material for biomedical applications. It was interesting that the system kept in liquid status for a long time near 4 A degrees C and transformed rapidly to gel status within 1 min upon heating to 37 A degrees C. The hydrogel could be dissolved at acid pH, while it absorbed water at neutral and basic conditions. The release of BSA from TMC/beta-GP gels was slow at neutral pH. The TMC/beta-GP hydrogel is a promising vehicle for the drug release, tissue repairing and regeneration.