A carotenoprotein from the muscle of Ascidian (Halocynihia roretzi) was purified by ion exchange chromatography and gel filtration chromatography, and analyzed molecular weight, stability of pH and heat, effect of denaturing agents, amino acids and fatty acids composition. The purified carotenopotein had absorption maxima of 463 ㎚ and 439 ㎚. The carotenoprotein had an approxmimate molecular weight of 64.4 kDa in polyacryl-amide gel electrophoresis. The amino acid compositions of carotenoprotein were mainly Gly(15.39%), Asn(11.31%), Gln(10.62%) and Ser(13.35%). The major fatty acids composition of carotenoprotein were C◎(15.4%), C◎(14.5%) and C_(20:1(n-11))(11.4%). The monounsaturated fatty acids(45.2%) contained abundant content compared to other saturated(38.1%) and polyunsaturated(11.7%) fatty acids.