Few researches have been performed on the circadian rhythm of oxidants and anti-oxidants and these studies have demonstrated different results. The aim of this study was to investigate the circadian variation of MDA, PC and SOD in non-athlete young men. The research method of this study was semi-experimental. For this purpose, 10 non-athlete active students (mean age: 23.2±2.57 years old, height: 174.5±6.35 cm and weight: 65.9±4.5 kg) from Tabriz University voluntarily participated in this study. All participants performed the protocol of diurnal activity, nocturnal rest, meals and physical activity for two weeks. The day before the blood sampling, all participants were present in the laboratory and spent the night under the supervision of the researcher. The researcher controlled their diurnal activity, nocturnal rest and meals before and during the research for 48 hours. The subjects woke up at 08:00 and slept at midnight with three similar meals served at 08:15, 13:30 and 21:30. Six blood samples (4 cc) were collected from noon for 24 hours with 4-hour intervals. The samples were sent to the laboratory to examine MDA, PC and SOD. Data were analyzed by analysis of variance (ANOVA) with repeated measures. The results showed that MDA exhibited a significant circadian rhythm (P=0.014) while there was not a significant variation in SOD (P=0.089) and PC (P=0.808). But dependent t test showed a significant difference in some hours in SOD factor. The results of this study showed that there is a higher risk of oxidative stress in the morning. So, the stress exercise in the morning should be performed with higher attention.