The effects of frying oils’ fatty acid profile on quality, free radical and volatiles over deep-frying process were investigated, using oils with different fatty acid composition. Results showed oxidative stability of frying sunflower oil (SO) were higher than that of frying palm oil (PO). Meanwhile, free radicals in frying oils increased over frying time, and amounts of free radicals in SO were higher than those in PO. Our further analysis on fatty acid composition showed oleic and linoleic acid decreased significantly with the increasing frying time, indicating unsaturated fatty acid of oils degraded under frying process, while no significant change of saturated fatty acids was observed. Results of volatiles indicated that totals of 27 main volatile compounds were found in both frying oils but their content distributed differently in two oils. Chemometrics analysis showed that (E,E)-2,4-octadienal, (E)-2-decenal, 2-undecenal, 1-heptanol, 1-octanol, 2-undecanol, 3-hepten-2-one, 1-undecanol, octanoic acid, nonanoic acid, octane, dodecane and tetradecane was highly correlated with AV, POV, p-AV, PCs and free radical in frying PO, while (E)-2-hexenal, 1-nonen-3-ol, 2-dodecanol,3-methyl-3-buten-2-one, 4-methyl-2-hexanone, pentanoic acid and nonadecane was highly correlated with quality indices in frying SO, indicating these volatiles may be proposed as potential indicators for evaluating lipid oxidation of corresponding frying oil. •Application of EPR with DMPO as spin trap in thermal oxidation of frying oils.•Volatiles of frying palm and sunflower oil were formed by oxidation of fatty acids.•Potential volatile indicators for evaluating oxidation differed in different oils.•Chemometrics analysis was used for finding volatile markers for quality evaluation.