The invention relates to a determination method for inorganic arsenic in aquatic products. After being extracted by hydrochloric acid solution, the inorganic arsenic (1plus1) in the aquatic products passes through an anion-exchange column, and arsenite As (III), dimethyl arsenic compound DMA, methyl arsenic compound MMA and arsenate As (V) are eluted sequentially by mobile phase; owing to different adsorption capacities of the anion-exchange column on the arsenate As (V), the arsenite As (III), the methyl arsenic compound MMA, the dimethyl arsenic compound DMA and arsenic sugar AsS, the eluted solution is hydrogenated by borohydride potassium reducing agent and hydrochloride, and hydride is generated, enters an atomizer, and is subject to analytic determination by being combined with atomic fluorescence. The experimental condition is reasonably selected, and the detecting data is accurate and reliable and can not be influenced by extraction time and temperature. The determination method of inorganic arsenic in aquatic products of the invention not only can detect the inorganic arsenic iAs accurately, but also can determine the methyl arsenic compound MMA and the dimethyl arsenic compound DMA of the organic arsenic, and can be used for the morphometry of the arsenic in the aquatic products.