In order to study the effect of deficit IRRIGATION and bio-fertilizer on potato cultivars, a field experiment was conducted at Ardabil Agricultural and Natural Research Center, Iran, in year 2014. Water deficit stress set as main factor with three levels, I1 (full IRRIGATION), I2 (0. 8 full IRRIGATION) and I3 (0. 6 full IRRIGATION, three genotypes set as split plot and bio fertilizer set as split split plot based on randomized complete block design with three replications. Adjectives such as emergence and flowering time, plant height, main stem diameter, number of stem, leaf and stem dry weight, chlorophyll and carotenoid content and plant yield were studied. Results indicated that all traits significantly affected by IRRIGATION treatments, exception number of branches. Emergence, flowering date, plant height, stem diameter, number of branches and plant yield had significant differences among genotypes. Effect of interactions between IRRIGATION and genotype were significant on stem diameter only. Bio fertilizer increased amount of all traits as plant yield increased in 10 percent proportion compared with control. The highest potato yield was obtained in Clone 97-2. The highest yield obtained with full IRRIGATION and potato yield decreased 40 percent by severe water stress compared with control. Therefore using of bio fertilizer recommended as supplement fertilizer for potato.