A study was carried out to determine arsenic species in seafood samples collected from Chinese sea. The information about arsenic species in samples was provided by high performance liquid chromatography-inductively coupled plasma mass spectrometer (HPLC ICP MS) and electrospray tandem mass spectrometry (ES MS MS). The arsenic species in thirty Chinese edible seafoods, including algae, fish, crab, shrimp, mussels, oysters, and clams popularly ingested by Chinese people as regular foods, were examined in the present report. Arsenosugars were detected in all of the extracted algae samples (1 5—33 8μg·g -1 dry weight) and some shellfish samples (0 018—0 78μg·g -1 wet weight). Arsenobetaine was detected in all of the extracted fish and shellfish samples (0 025—6 604μg·g -1 wet weight). In contrast, inorganic arsenic was only present in the examined fish and shellfish samples, at levels less than 2% of the total arsenic. The study provides information about a possible distribution pattern of arsenic species in seafood products.