Abstarct: In the recent years global demand for the medicinal herbs such as peppermint is increasing, the use of microorganisms that have a symbiotic relationship with plants and plant growth regulators are a new strategy to improve the environmental performance of the plants in adverse conditions such as saline water and soil. In this study, therfore, the symbiotic effect of mycorrhiza like fungi, Piriformospora indica, on the growth improvement of peppermint was designed and implemented under salt conditions. This research was conducted in both greenhouse and farm, conducted with factorial arrangement baxsed randomized complete block design with three replications at the greenhouse and farm of agricultural was conducted in order to achieve the desired goals. The first factor was the treatment of fungi inoculation (inoculated and uninoculated control); the second factor, methyl jasmonat foliar, in the pot experiment including (0, 75, 150μM), in the farm experiment was methyl jasmonat foliar in 2 concentrations (0 and 750μM), and the third factor, four salinity levels (0, 3, 6, 9 dS m-1). The results showed that under salt stress, P.indica inoculation, plant growth, essence content, relative water contents, Photosynthetic pigments, fluorescence parameter (except NPQ and Fo), stomatal conductance and , transpiration, mineral elements P and K accumulation in leaf was decreased the activity of antioxidant enzymes, MDA content, membrane electrolyte leakage, soluble carbohydrate and Na accumulation in leaf showed significant increase. In field and pot experiment, the most of negative effects was observed in 6 and 9 dsm-1. In field and pot experiment, P.indica inoculation had the positive impact on the reduction of Na accumulation in leaf, maintaining chlorophyll, increasing essential oil content and composition, total phenol, anthocyanin and radical scavenging DPPH, reducing lipid peroxidation of membranes and growth improvement and element uptak and increased the activity of antioxidant enzymes under salt stress. In pot experiment, MJ treatment by the concentration of 150 μM significantly increased effect of salinity on the P.indica inoculation, RWC, membrane lipid peroxidation, chlorophyll concentration and ETR. Results of greenhouse and field study showed that MJ (75 μM) application reduced the negative effect of salt stress, and increased essential oil content and menthol in non-stress condition. Combined P.indica and MJ application had the most alleviating effect in pot experiment on, menthol, total phenol, catalase, P, reducing the concentration of MDA, and in field experiment was recorded in shoot dry weight. So it seems that symbiosis with fungi P. indica and application of MJ (75 μM) caused against the negative effect of salinity by improvement in physiological and growth processes leading to the tolerance of the plant to salt stress.