Abstract: Protein glutaminase（PG）is an enzyme that catalyzes the specific hydrolysis of glutaminyl residues in proteins and peptide. The metabolic pattern of Chryseobacterium indologenes in PG synthesis and primary purification of PG were studied. The pH value and ammonia concentration increased during the fermentation. The maximal PG activity reached 0.359 U/mL for 14 hours culture. The efficiency of purification and yield of PG were maximal when culture borth was centrifuged and the supernatant was concentrated for four times by ultrafiltration with 3 kD cut-off membrane. Ultrafiltrate was precipitated by 4 times volumes ethanol and the maximal yield of PG was 72.7%. Precipitated PG by ethanol was dissolved in PBS buffer and further purified by SP-Sepharose Fast Flow ion-exchange chromatography. A single peak was got in elution profile. The final yield of PG was 31.72% and the PG was purified 124 times after multiple purification steps. The purified sample contained a single band in SDS-PAGE and corresponding molecular weight was about 20 kD.