China is a big country with seaweed production, and seaweed is the peoples favorite health food. However, since the new sanitation standard and testing standards were issued, in accordance with the new testing standards, we found that the over-standard of inorganic arsenic was very serious in the seaweed. In order to explore its cause, this paper surveyed the inorganic arsenic content of some seaweed products such as laver and kelp which come from home and abroad, and we also carried out tracking detection the determination of inorganic arsenic of the different harvest period fresh laver and the laver products, and aquaculture regional water. We found that in accordance with the new sanitation standard and testing standards, the over-standard of inorganic arsenic was a common problem; it was related to the inorganic arsenic content of aquaculture regional water, but not a linear relationship. In the experimentation, we used two methods of the GB/T5009.11 to determinate the inorganic arsenic in seaweed, the distinction of data was very greatly. And these two method were all not suitable to determinate the inorganic arsenic in seaweed.