Seal oil is a new source of functional fatty acids， besides being rich in DHA and EPA， also contains another important fatty acid-DPA. Therefore， seal oil has good health function. Refining and esterification are important processes for high purity functional oil， which exert important influences on the product quality. Hence， it is of great significance to study the quality changes during the processes. In this paper， the effects of refining and esterification on the quality of seal oil were evaluated by physicochemical index， fatty acid composition and volatile substance， which were determined through physicochemical analysis， GC and HS-SPME-GC-MS. The results showed that refining could significantly reduce the moisture content and volatile matter （1.65% to 0.49%） and acid value （3.11 mg KOH/g reduced to 0.63 mg KOH/g）， while had no significant effect on the peroxide value. Refining and esterification reduced the content of MUFA while improved SFA and trans-fatty acid content （C18：1 trans， C18：2 trans）， had little effect on the content of EPA， DPA and DHA. 86， 50 and 44 volatile substances were detected in seal oil crude oil， refined oil and ester oil， respectively， and the total peak area of volatile substances were 83.16%， 60.06% and 36.19%， respectively. This indicated that refining significantly reduced the type and content of volatile substances while the esterification significantly reduced the content of volatile substances.