The effect of seed rate of alfalfa (Medicago sativa L.) and efficiency of plant growth promoting bacteria (PGPR) that facilitates phosphorus uptake with different doses of phosphate fertilizer was evaluated on seed quality. For this purpose, the germination and seed vigor tests before and after accelerated aging were performed in a split split plot experiment based on randomized complete block design with three replications in 2010 in the field of education and research in the College of Agriculture and Natural Resources, Tehran University, Karaj. Phosphorus factor at 4 levels (0, 30, 60 and 90 kg Phosphorus.ha-1) in main plots, PGPR (Pseudomonas) in three levels (no bacteria, bacterial strains, No. 9 and bacterial strains No. 41) in subplots and rate of seed factors on three levels (2, 6, and 10 kg of seed per hectare) were the sub-subplots. The results showed the highest rate of germination and seed vigor obtained by use of 6 kg seeds per hectare, PGPR No.41 strains with 30 kg Phosphorus per hectare and after accelerated aging. The highest rate of germination and seed vigor at 10 kg of seed per hectare were found for PGPR No.41 strains, with 60 kg Phosphorus ha-1 treatments. After accelerated aging practices to achieve maximum germination index and vigor, seed rates and phosphorus requirement were more than standard conditions. Based on obtained results for the storage conditions, bacterial strains No. 41 had a better effect on increasing seed vigor than bacterial strains No. 9. To produce alfalfa seed with high vigor and obtain better results, use of optimum seed rates and phosphorus (6 and 30 kg.ha-1, respectively) along with PGPR (strain No. 41) could be considered in crop plants.