In order to investigate poly(N-vinyl pyrrolidone) as an alternative to poly(ethylene glycol) in preparing a biomedical polymer, we synthesized a series of reverse thermogelling poly(N-vinyl pyrrolidone-b-alanine) (PVP-PA). The amphiphilic polymers consisting of the hydrophilic PVP block and the hydrophobic PA block formed micelles in water and the micelles aggregated as the temperature increased. FTIR spectroscopy, circular dichrosim spectroscopy, and C-13 NMR spectroscopy showed that the aggregation behavior accompanied a change in PA conformation as well as a decrease in the molecular motion of PVPPA. The sol-to-gel transition temperature decreased as the PA block length increased, PVP block length decreased, and L-alanine/DL-alanine ratio of PA increased. This paper suggests that PVP can be a promising alternative to poly(ethylene glycol) in designing a reverse thermogelling biomaterial.