[Objective] To identify a protease producing bacterium CAU342A isolated from soy sauce koji and optimize the fermentation conditions for protease production. [Methods] Strain CAU342A was identified based on its morphological characters, 16S rRNA gene sequence, physiological and biochemical characteristics. The fermentation conditions for protease production by strain CAU342A were optimized using the one-factor-at-a-time method and orthogonal test. [Results] strain CAU342A was identified as Pseudomonas aeruginosa, and the optimal fermentation conditions were obtained as follows: 3% vinasse, 1.5% yeast extract, 0.05% Tween-80, 0.5% NaCl, 0.7% K2HPO4, 0.3% KH2PO4, 0.04% MnSO4, the initial pH was 7.5 and incubation temperature was 30 °C for 72 h. Under the optimized fermentation conditions, the highest protease activity of 2 653.5 U/mL was achieved. The protease zymogram analysis showed that at least 4 proteases were secreted into the fermentation broth, and two major bands had molecular masses of 32 kD and 50 kD, respectively. [Conclusion] The high-level production of protease by Pseudomonas aeruginosa CAU342A enables its potential industrial applications.