Abstract: The recent development of scientific researches on Molecular Toxicology of arsenic is briefly reviewed.The main contents of this paper include;(1)Effects of arsenic on synthesis of large biological molecules, including studies on rates of synthes is of DNA, RNA, proteins, and heat shock proteins, and accuracy of DNA synthesis, and hydrolysis of proteins, and so on;(2)Effects of arsenic on DNA damage and repair,emphasizing investigations on effects of arsencin E.coli and in human cells;(3)The newest studies on effects of arsenic on geneamplification and blast transformation of human lolld lymphocytes. We suggest that arsenic might be a necessary biological super-traceel ementf or lief,and further studying this problem is needed.