The quality of the oil extracted from rainbow trout (Oncorhynchus mykiss) wastes was evaluated using bioactive compounds of the plant thyme (Zataria multiflora). Three treatments were in this research: 1- Samples without extract or essence (control), 2-Samples with concentrations of 600 and 1200 ppm of extract and 3-Samples with concentrations of 600 and 1200 ppm of essence. The oil samples entered in test tubes which rapped in aluminum sheets and incubated in 50° C and analyzed on days 0, 3, 6 and 9. The results showed that chemical analysis of oils extracted from rainbow trout wastes including peroxide and non-enzymatic browning were lowest in 1200ppm of essence on day 9 of storage period while some other quantitative indices including thiobabrbitoric acid, free fatty acids and anisidine value were lowest in 600ppm of extract and essence on day 9. Comparing quantitative parameters in control and other treatments showed that almost all indices were higher in control indicating the antioxidant activity of the extract and essence of the plant they in reducing oxidative spoilage rate and increasing the shelf life of the oils.