This paper reported and compared macronutrient components of six species of marine and freshwater shellfish in China. Marine shellfish species included 〖Crassostrea ariakensis (the Jinjiang or Asian oyster), Solen strictus (razor clam), and Paphia undulata (shortnecked clam or undulated surf clam). Freshwater species were Anodonta woodiana (Chinese pond mussel, the Eastern Asiatic freshwater clam or swanmussel), Cipangopaludina cathayensis (river snail), and Bellamya purificata (mud snail). No significant differences were found in water content of edible portions among all species except the Chinese pond mussel. However, remarkable differences were detected in contents of crude protein, lipid, and ash. Razor and shortnecked clam was classified as shellfish with high protein, containing approximately 75% protein, 8% lipid, and 14% ash (at dry mass), respectively. Chinese pond mussel and the Jinjiang oyster belonged to shellfish species rich in lipid (14% lipid, 50% protein, and 6% ash). River and mud snails were grouped as shellfish with high ash (30% ash, 60% protein, and 3% lipid). Based on amino acid scores, protein quality of these shellfish was slightly lower than whole egg protein in general. However, score of lysine was higher than that of whole egg protein, indicating that shellfish meat can exert better complementary effects of proteins if combining with food stuffs in lack of lysine especially grains and cereals. Regarding lipid quality, marine shellfish showed more advantages than freshwater species since the former contained higher polyunsaturated fatty acids especially eicosapentaenoic acid (EPA) and docosahaenoic acid (DHA) than the latter. The total amount of EPA and DHA in razor and shortnecked clams, and the Jinjiang oyster was 14.19%, 25.51% and 34.29%, respectively. However, no EPA or DHA was detected in river snail. In mineral nutrients, two species of snails possessed promising potential and might be applied in development of natural dietary supplements for minerals. This study provided useful information for consumers during decision on shellfish selection according to their nutritional requirements (fit for purpose).