Objective To study the changes of acid value, benzo [a] pyrene, 4 kinds of polycyclic aromatic hydrocarbons (PAH4) and 16 kinds of polycyclic aromatic hydrocarbons (PAH16) content in frying french fries soybean oil/peanut oil at different temperatures and times. Methods The acid value in oils was titrated by anhydrous ether:isopropanol (1:1, V:V) using phenolphthalein as an indicator. The polycyclic aromatic hydrocarbons in samples were saponified by KOH/ethanol, extracted with n-hexane and cleaned-up by solid-phase extraction column, detected by gas chromatography-mass spectrometer. Results With the increase of frying temperature and time, the acid value increased rapidly, and the changes in peanut oil were more sensitive. At the same temperature, both benzo [a] pyrene and PAH4 showed an irregular fluctuating growth with time, and the higher the temperature, the faster the increase. The content of PAH16 rapidly increased with time and temperature, and its changes were more sensitive than those of benzo [a] pyrene and PAH4. Under the same conditions, the increase of benzo [a] pyrene, PAH4 and PAH16 in peanut oil was less than that in soybean oil. Conclusion At the same conditions, PAH16 shows more significant changes compared to benzo [a] pyrene and PAH4, so the limits of PAH16 should be given more attention.