Abstarct: This study had been performed to assess the effect of inoculated thiobacillus and rhizobium bacteria and different levels of nitrogen fertilizer on cowpea. To the same, a factorial test in a complete randomized block design with three replications was conducted in Shahrood University in 1392. Studied Factors were: thiobacillus bacteria (consumption and non consumption), rhizobium bacteria(consumption and non consumption) and nitrogen fertilizer in four levels(0-70-140-210 kg per ha), in the weed and non weed presenseconditions. Results showed that the triple effect mutual nitrogen fertilizer, inoculated thiobacillus and rhizobium bacteria had significant impact on grain yield, biological yield, grain weight, number of leaves per plant, number of grain per plant, chlorophyll A, chlorophyll B, carotenoid and RWC in weed conditions and grain yield, biological yield, number f pods per plant, grain weight, number of leaves per plant, number of grain per plant, chlorophyll A, carotenoid and RWC in non weed conditions. The most of grain yield in weed conditions attendance use nitrogen fertilizer (210kg per ha) and inoculated percent increase compared to the witness plant. The least of grain yield in weed conditions was attendance non use nitrogen fertilizer and non inoculated thiobacillus and rhizobium bacteria amount; 190/642 kg per ha. The most of grain yield in non weed conditions attendance use nitrogen fertilizer (210kg per ha) and inoculated thiobacillus and rhizobium bacteria amount; 500 kg per ha and 24/89 percent increase compared to the witness. The least of grain yield in non weed conditions was Attendance non use nitrogen fertilizer and non inoculated thiobacillus and rhizobium bacteria amount of the 160/558 kg per ha. The most of biologycal yield in weed conditions attendance use nitrogen fertilizer (210kg per ha) and 1789/344 kg per ha and 63 percent increase compared to the witness. The least of grain yield in weed conditions was Attendance non use nitrogen fertilizer and non inoculated thiobacillus and rhizobium bacteria amount of the 780/634 kg per ha. The most of biologycal yield in non weed conditions attendance use nitrogen fertilizer (210kg per ha) and inoculated thiobacillus and rhizobium bacteria amount 1230/625 kg per ha and 22/5 percent increase compared witness. The least of grain yield in non weed conditions was attendance non use nitrogen fertilizer and non inoculated thiobacillus and rhizobium bacteria amount 750/85 kg per ha.