Abstract: To search for a high catalase-producing bacteria strain, field samples and lab collections were screened. FZSF02 was initially selected and subjected to morphological examinations and 16S rRNA sequencing.It was identified to be a strain of Serratia marcescens. Subsequently, various carbon and nitrogen sources, mineral salts, and fermentation conditions to maximize the catalase production of the bacteria were experimented and optimized. It was found that a medium consisting of 1% soy peptone, 0.5% lactose, and 0.2% NaCl applied for the fermentation at 31℃ with a constant shaking at 180rpm for 48 h could yield the enzyme at the highest level of 6 380 U·mL^-1 among all tested conditions. The yield was 7.4 times of what was without the optimization. The peak activity of the obtained crude catalase was determined to reach at 60℃ and pH 8.0.The enzyme could potentially be applied for treating hydrogen peroxide pollutionin waste water effluent.