In order to determine the position and the content of fatty acids sttached to glycerides and the migration degree of fatty acids in the migration reaction, fish oil was hydroyzed with lipolase-100T which was derived from Aspergillus oryzae. The content of fatty acids in the glyceride mixture was analyzed and compared with that of fish oil. The amounts of fatty acid in a 2-position and the migration degree of the fatty acid in 2,3-DG (diglyceride) and 2-MG (monolyceride) were carefully calculated. The results showed that approximately 95% (w/w) of DHA (docosahexanoic acid) and 65% of EPA(eicosapentaenoic acid) were attached to the 2-position of glycerides in fish oil. Approximately 87% (w/w) of DHA and 75% of EPA remained in 2,3-DG, and 88% of DHA and 65% of EPA in 2-MG were not involved in the migration reaction.