Abstarct: Stachys lavandulifolia Vahl (Mountain tea) is the main species of genus Stachys L which wildly grows in Iran. S.lavandulifolia has many medicinal and antioxidant properties. In this study Response Surface Methodology (RSM) was used in order to evaluated the effect of extraction condition (power of ultrasound, solvent to solid ratio, time and solvent concentration) on Total Phenolic Content (TPC), Total Flavonoid Content (TFC), Antioxidant Acticity (AA), Antioxidant Activity per mg TPC (AA/mgTPC) and Antioxidant Activity per mg TFC (AA/mgTFC). According to The results of analysis of variance table (ANOVA) the polynomial quadratic equation was the best model for describing the optimum conditions. The optimum extraction conditions were as follows: power: 300W, solvent to solid ratio: 40/1, time: 14 min and concentration 60%. The responses, which including: TPC, TFC, AA, AA/mgTPC and AA/mgTFC in optimum conditions were as follows: 16.59±0.18 (mg Gallic acid/g DW), 44.81±0.79 (mgQuercetin/g DW), 80±0.39% 4.82% and 1.78% respectively. Antioxidant properties, such as ferric reducing ability and total antioxidant capacity and also IC50 value in optimum conditions were measured which result as follows: 0.004±0.0001 (absorbance per 0.1 mg phenol), 14.61(mgBHT/g DW), and 4.03 (μg Gallic acid) respectively. Phenolic compounds of S.lavandulifolia extracted were analysed with LC-ESI-MS/MS which 45 compounds were identified.