Soil contamination by cadmium is a limiting factor for growth and yield of crops worldwide. Phytoremediation, is considered as a cost effective and environmental friendly for remediation of contaminated soils with heavy metals. The efficiency of this method depends on plant species, interaction between plant roots and rhizospheric microorganisms and concentration of heavy metals in soil. Some soil microorganisms including bacteria and fungi have a strong stimulatory effect on plant growth and increasing plant resistance to environmental stresses. This study was conducted to investigate the influence of individual and combined inoculation of plant growth promoting microorganisms including an endophytic fungus Piriformospora indica , Mycorrhizal fungus (G.intraradices) and Sinorhizobium meliloti on some growth parameters of alfalfa ( Medicago sative ) and activity of some soil enzymes under cadmium pollution stress. For this purpose, a greenhouse experiment using a completely randomized factorial treatments including cadmium (0, 50, 100 mg/kg cd) , mycorrhizal fungus (inoculated and non-inoculated), P.indica (inoculated and non-inoculated) and Sinorhizobium meliloti (inoculated and non-inoculated) were conducted on three replicates in pots containing non-sterille soil at Isfahan university of technology. The results showed that with increasing cadmium stress ( increasing the concentration of soil cadmium from 50 to 100 mg/kg) , wet and dry weight, shoot height, chlorophyll content, L-glutaminase urease activity and nitrogen concentration in shoots of control plants decreased but shoot phosphorus and shoot and root cadmium concentration of these plants increased. Individual inoculatation of G.intraradices had the greatest impact on root dry weight under cadmium stress conditions. This treatment at levels of 50 and 100 cadmium increased root dry weight respectively, 25% and 13% compared to the control. Individual treatments of all studied microorganisms increased shoot dry weight at all levels of cadmium compared to the control. Co- inoculation of G.intraradise and Sino rhizobium meliloti in hight cadmium stress (100 mg/kg Cd) had the greatest effect on shoot dry weight among all co-inoculation treatments. Also under such conditions, S.meliloti treatment was the most effective treatment in increasing height and shoot fresh weight, so that hight and shoot fresh weight of inoculated plant with this bacterium were 45% and 22% greater than the control plants, respectively. Individual treatment of S.meliloti at 0, 50, 100 mg/kg Cd increased chlorophyll content 13%, 8% and 12% compared to the control , respectively. Individual treatments of the three microorganisms at all levels of cadmium increased shoot phosphorus and nitrogen compared to the control. Maximum L-glutaminase activity was reported in inoculated plants with G.intraradices under cadmium non polluted conditions. The increased of L-glutaminase activity of rhizospheric soil of inoculated plants with mycorrhizal fungus at cadmium level of 0, 50, 100 (mg/kg) in comparison with the control plants was reported 20%, 24% and 18% respectively. Among the individual microorganisms treatments, the most effective treatment in increasing urease activity at cadmium levels of 0, 50 (mg/kg) was mycorrhizal fungus and at cadmium level of 100 (mg/kg) the bacterium treatment was introduc