The effect of three isolated Phosphate Solubilizing Bacteria (PSB) on several growth indicators of potao Var. Agria was investigated in two experimental fields located in Arak and Karaj. In both locations,and RCBD on facteriel designs experiments were replicated three times. Variables were three levels of amonium phosphate fertilizer (0, 50, 100 kg/Hec) and four bacterial (B1 to B4) treatments. Bacteria solution were directly applied to the potato tubers either by sperying or by soaking. Analysis of Variance (ANOVA) for the yeild of potato shows that there is significance difference among treatments. Consistantly, the highest yeild was obtained by the use of Barvar-2 (B3) treatment in both locations. Despite significant difference between two location, combined ANOVA was also indicative of positive effect of Barvar-2 bioferilizer. However, the early growth rate of the potato plants did not affected significantly.Similar results were achived for combined ANOVA for interactions between treatments with chemical and biological fertilizers. The use of 50 to 100 kg/Hec amonium phosphate fertilizer along with Barvar-2 produced the highest yeild in Karaj and Arak. These suggest that bacteria may help the oiptimal use of phosphate fertilizers as well as insoluable phosphorus that exist in the soil.