Abstract：Forty-one coal samples collected from Southwestern were measured.The mean of arsenic in Southwestern coals is 7.03mg/kg.The level of arsenic contents is higher than China coals and world coals.From the result, the richest content of arsenic is located in Yunnan province.In three main coal-forming periods, the arsenic contents decrease from Tertiary, Late Triassic to Late Permian.Moreover, the enrichment factors and the occurrence of arsenic were analyzed in the paper.The results show that the main factor is tectonic movement and the occurrence of arsenic is various.

Keyword：coal;arsenic;coal-forming period;occurrence;