It is an important point about the inorganic arsenic in the alga outside the standard, yet there is not any negative news about eating the alga leads toxicosis. We detects the inorganic-arsenic in samples and the standard organic-arsenic we bought from America with GB/T5009.11-2003, the results tell us this two organic-arsenic effect the value of inorganic-arsenic in alga. It is transformed from organic-arsenic to inorganic-arsenic.