Since the ultimate goal in the cultivation of medicinal plants is to achieve secondary metabolites, Phosphorus is one of the macro nutrients and plays an important role in plant growth and essential oil biosynthesis that its deficiency reduces the growth and function of the plant. In order to evaluate the effect of phosphorus deficiency on growth factors and essential oil quality of Salvia officinalis L. and Mentha aquatica L. an experiment was conducted in a completely randomized design with three replications including phosphorus treatment at two levels of control and phosphorus deficiency on Salvia officinalis L. and Mentha aquatica L. plants. Phosphorous deficiency caused decrease in growth factors in both plants. Mean comparisons showed that phosphorus deficiency decreased root and shoot length and dry weights in Salvia and Mentha. There was a significant positive correlation between shoot dry weight and shoot length (P<0.01, r= 0.875) and leaf area (P<0.01, r= 0.914). Therefore, according to the results it seems that P deficiency in a controlled way can increase the essential oil content by increasing the content of some essential oil components in Salvia and Mentha.