Abstract: In order to explore the best linseed oil physical refining process conditions, the differences impact on refined linseed oil quality between physical refining process and chemical refining process were compared. Taken pressed linseed oil as raw material, which had 55% linolenic acid, the content of trans-acid and the law of linseed oil quality in the oil refining process were studied. The result showed that both chemical refining and physical refining technology could control the acid value below 0.3 mg/g. During chemical refining process, the content of the trans-acid in linseed oil remained was 0.2%-0.4%; while during physical refining process, under the condition of 200℃, absolute pressure 10-50 Pa, the content of trans-acid obviously changed. The content of trans-acid in bleaching oil was 0.27%, while the content of trans-acid were 0.91% and 1.73%, respectively, after four hours and eight hours physical refining process. The result also showed that the oil quality in chemical refining process changed slightly and the peroxide value was 4.1 mmol/kg, while in physical refining process the peroxide value at the first six hours was less than 6 mmol/kg and increased slowly.