Abstract: Pseudomonas sp. IOFA1， the strain isolated from the deep-sea sediments of Indian Ocean， was found to degrade formaldehyde efficiently. IOFA1 could rapidly degrade 100mg/cm³ formaldehyde within 40 min. The crude enzymes in cell lysate were purified with a DEAD-sepharose ion exchange column and analyzed with SDS-PAGE. After segregation， a pure protein with formaldehyde-degrading activity was obtained and was further identified as formaldehyde dismutase （FM11） by MALDI-TOF/TOF mass spectrum. Sequence analysis showed that FM11 shared 65% maximum amino acid sequence identity to known formaldehyde dismutase from other species. Domain analysis suggested the existence of two conserved zinc atom binding sites and one conserved NAD binding site in FM11. FM11 was most active at 40℃ and retained more than 95% of its maximum activity at temperatures ranging from 25℃ to 60℃， exhibiting well adaption to temperatures. FM11 displayed a broad range of optimal pHs （pH 5~9）， and could adapt to wide pH environments as it could retained more than 50% and 80% of its maximum activity in pH 4 and pH 10， respectively. FM11 could retained more than 97% and 90% of its initial activity after incubation for 1 h in pH 5~7 and pH 7~10 environments， respectively， displaying a excellent acidic and alkaline stability. The presence of Ca²⁺、Mg²⁺⁺ at low concentration could significantly increase the activity of FM11. Collectively， our findings should provide a foundation for the utilization of Pseudomonas sp. formaldehyde dismutase in the decontamination of environmental formaldehyde．