Recently, culture of Undaria pinnatifida, one of the representative esculent sea weed, has been prevailing in tile east and south coasta of Korea and reached the mass culture stage. In this study, compositional quality factors for food were studied and the contributory effects of blanching and pigment fixatives in the quality retention of cultured Undaria pinnatifida are discussed. When the place and time of harvesting were the same, cultured pinnatifida showed scarce difference in the chemical composition comparing to tile naturally grown Undaria pinnatifida, but cultured Undaria pinnatifida shelved a considerable difference depending upon the cultured places. In the chemical composition of Undaria pinnatifida, the alginic acid comprising about $40\%$ of the whole solid materials seemed to be responsible for the compositional puality. The chlorophyll and carotenoid content of the clutured Unaria pinnatifida were considerably lower than that of the naturally grown Undaria pinnatifida and wass inferior in puality by color to the naturally grown one. Dried Undaria pinnatifida contained a considerable amount of amino-N, mannitol, and soluble minerals and it is considered that these components play a great role in the relish effects. It could also be evaluated as a good albuminous source for food science the dried pinnatifida contains about $18\%$ of crude protein. In the analysis of free amino acid composition of dried Undaria pinnatifida, the naturally growm samples showed so what higher levels in all amino acid content than the cultured samples. The contents of theronine, alanine, and glutamic acid were major in quantity wherease histidine cysteine, tyrosine, and phenylalanine were minor. The contents of such amino acids like serine and proline were particularly low or undetectable. The results of amino acid analysis of the acid hydrolysates of dried Undaria pinnatifida in quantity of individual amino acid showed te same pattern as that of free amino acid. It is noticed that Undaria pinnatifida seemed to contain good quality protein since the contents of essential amino acids were considerably higher and uniform. By blanching the fresh sample, the water soluble components brought about cousiderable loss, and, particularly, it was noteworthy that both mannitol and soluble minerals apparently decreased. In the pigment analysis of the dried sample, blanching was effective to retain chlorophyll and carotenoid. The addition of pigment fixatives in blanching solution such as Ca-gluconate, Ca-carbonate, and Ca-hydroxide did not exhibit much effect on the pigment retention except that Ca-carbonate shelved some effect only in the early stage of storage.