Abstract: Based on the analysis of 15 raw coals and washed coals collected from Southwestern, the washing rate of arsenic, sulfur and ash from raw coals was studied. The average washing rate of arsenic in raw coal is 38%. Arsenic of raw coals is mainly associated with pyrite and sulfide. However, arsenic of some raw coals is mainly or wholly associated with organic matter and mineral enwrapped by organic matter. It is difficult to remove such part of arsenic and it will enrich in the washed coals. The results show that there is a little relationship between occurrence mode of arsenic associated with organic sulfur and rank of coal, but it is complicated with age of coal-bearing strata.