The invention discloses an aerobic arsenic methylation bacterium SM-1 of cytophagaceae and application of the arsenic methylation bacterium. A gram-negative bacterium, which is quite strong in arsenic methylation and volatilization capacities, is obtained through isolation and identification; and the strain belongs to a new genus and a new species of the cytophagaceae, which is named as arsenicibacter palustris SM-1 and preserved in China Center for Type Culture Collection on October 15, 2014 with preservation number of CCTCC M2014457. Compared with the prior art, the bacterium disclosed by the invention has the following beneficial effects: the provided bacterium strain is quite strong in arsenic methylation and volatilization capacities; and the strain is applicable to arsenic pollution remediation of paddy soil and is capable of finally relieving the damage from arsenic pollution in a paddy field.