Introduction: Organophosphorus compounds are the most important and most widely used insecticides and malathion is one of this toxins that has been used in the world widely. Oxidative stress and nitrosative stress are the new mechanisms of these compounds. The aim of this study was evaluate the effect of malathion on nitrotyrosins’ cosentration in rat liver.Material and Methods: In this experimental study 12 male wistar rats with 180-250grs were separated into case and control equal groups. Case group administrated 200mg/kg/day for a week and control group have normal salin at this course. Then rats’ livers were homogenized and biomarkers of nitrotyrosin were measured by ElIZA test in them. The statistical software used for this analysis was SPSS version 16 and P< 0.05 was considered as the minimum level of significance.Results: Mean of nitrotyrosins’ biomarker in liver tissue for case group were 0.265±0.094nmol/mg protein reported and the mean of nitrotyrosins’ biomarker in liver tissue for control group were 0.180±0.007nmol/mg protein reported, p= 0.051.Conclusion: The Difference between two groups is very near to level of significance and mean of case group is more than control group, thus we result that malathion increase nitrotyrosin level and increase nitrosative stress in liver rat.