Abstract: There is no enough attention paid to arsenic pollution in atmosphere in China at present. The trace element arsenic in PM_2.5 was studied, with its harm, variation characteristics, pollution level, sources, control technology and standards analyzed. The results show that there are differences between arsenic and other metals in PM_2.5 in the rule of seasonal variation, someplace even showing almost the opposite trend. The daily variation of arsenic and PM_2.5 are positively related, while the spatial variation of arsenic is the same as other metal element. The arsenic pollution in PM_2.5 in China is serious, and there are some differences between northern and southern parts of the country. The relevant standard of arsenic in the air is lacking in China at present. Suggestions on arsenic pollution control and further researches were put forward based on the summarization of the variation, pollution level and control experience of arsenic in China.