Jar cheese is a hard, slightly acidic and sweet pungent that has a granular state and has a dry appearance. In this study, the effect of relative substitution of NaCl salt with KCl (0.25, 50 and 75%) on the characteristics of free fatty acids, fat, peroxide and acidity of Jar cheese was investigated. The results showed that replacing NaCl with KCl and ripening time (5, 45 and 90) did not have a significant effect on fat and peroxide levels (p> 0.05). The acidity content in different treatments did not change significantly with the replacement of NaCl with KCl, Acidity content was increased significantly during ripening period (p <0.05). The results of measurement of fatty acid profiles showed that butyric acid was detected in all treatments and its quantification was   in lowest amount within specific days of ripening period (5, 45 and 90). partial replacement of NaCl with KCl did not affect the free fatty acid profile except for stearic acid (C18), and also no significant changes were observed in total amount of free fatty acids measured among all treatments (p> 0.05). In terms of the overall acceptance sensory score, a significant difference was observed between the control treatment and the treatment containing (9% KCl + 3% NaCl) and the closest treatment to the control treatment in terms of the sensory score of flavor, texture, appearance and overall acceptance is the T1 treatment containing (3% KCl + 9% NaCl). In general, the results of this study showed that 50% NaCl can be substituted with KCl.