The change of palm oil index during the frying process of dace was evaluated by sensory and physicochemical analysis in this study, and the "Dalsorb adsorbent + plate filtration" method was used for palm oil treatment after frying. Results show that with the increase of frying time, the color of palm oil was gradually deepened, the liquidity and transparency were gradually degraded, and a large amount of fish dregs appeared. The acid value (from 0.06 mg KOH/g to 2.34 mg KOH/g), carbonyl value (from 3.64 meq/kg to 17.70 meq/kg) and polar component (3.07% to 15.1%) of palm oil increased with the increase of frying time, and there was no obvious change in the peroxide value. The change of acid value and polar component was closer to the upper limit of the national standard and could be used as evaluation index. In addition, the online monitoring should be mainly based on acid value index due to the reason for long detection time of the polar component. The "Dalsorb adsorbent + plate filtration" method could significantly reduce the acid value (from 2.36 mg KOH/g to 1.50 mg KOH/g), and the changes of carbonyl value and polar components were not obvious.