Effects of 0.02% L-ascorbyl palmitate（L-AP） on the kinetics of trans products of trilinolenin heated at 200-240 ℃ for 2-48 h were studied. Three kinds of single trans isomers（C18：3-9t，12c，15c， C18：3-9c，12t，15c and C18：3-9c，12c，15t） and two kinds of double trans isomers （C18：3-9t，12c，15t and C18：3-9t，12t，15c） were detected in heated trilinolenin analyzed by highly polar ionic liquid capillary columns. The formations of these trans isomers were zero-order reactions， and the reaction orders of these isomers were not changed by the addition of L-AP. L-AP could inhibit the formation rates of single and double trans isomers. The main role of L-AP was to inhibit the formation of single trans isomers， and the inhibit site was the isomerization of 15 hydrogen in linoleic acid chain， followed by 9 hydrogen 12 hydrogen. In addition， the forecasting model of thermally induced trans products concentration of trilinolenin， heating temperature and time were established in the presence of L-AP.