The molecular mechanism of the heat-induced cis / trans isomerization of non-conjugated linoleic acid （C18∶2） by alkali treatment and acid treatment was analyzed by gas chromatography with conventional heating as the control group. From the heating test， C18∶2-9c，12t and C18∶2-9t，12c are the main trans isomers in the heating of soybean oil. With the heating temperature gradually increased， the heating time gradually increased， the trans-linoleic acid content also increased， three kinds of oil samples after heating to produce trans fatty acids in the order： alkali treatment oil sample > acid treatment oil sample > Untreated oil sample. In the process of heating， the amount of monovalent linoleic acid produced is higher than the amount of bis-trans linoleic acid produced. When heated at 260 ℃ for 8 h， the amount of mono-functional linoleic acid （C18∶2-9c，12t） produced by heating oil after NaOH treatment， Up to 1.222%. It is found that C18∶2-9t and 12t are required to pass two energy barriers of 235.986 kJ/mol and 223.846 kJ/mol， respectively. The results showed that strong acid treatment or alkali treatment increased the chance of heating the trans isomers of oil， and the effect of strong alkali treatment was the strongest.