Abstarct: In order to study the effect of mycorrhizal fungi, nitrogen fixation bacter and nitrogen fertilizer on yield and yield components of soy beans, a field experimental was conducted during growing season of 2012 at the Technology University Agricultural Research Station located in Bastam. The experiment was a factorial experiment in the baxse of randomized complete blocks design with three replications. The factors were mycorrhizal inoculation (inoculated and non-inoculated with glomus intraradices), nitrogen fixation bacter inoculation (inoculated and non-inoculated with Rhizobium japonicum) and potassium fertilizer (0, 100 ,200 kg/hr). Growth analysis and leaf dry weight were measured with intervals of 15 days. Yield and yield components were analyzed at the end of the experiment. The results showed that the main effect of mycorrhizal on all variables other than seed weight, number of seeds per pod, number of pods per plant and seed yield was significant. The main effect of potassium fertilizer on all variables except for number of seeds per pod was significant. The main effect of rhizobium bacteria on all variables except for harvest index was significant. Interactions between mycorrhizal and rhizobium bacteria in plant hieght, number of pods per plant, percent oil and mycorrhizal colonization of roots was significant. rhizobium bacteria, mycorrhizal fungi and potassium fertilizer, increased growth index compare to control. Mycorrhizal fungi and potassium fertilizer had a greater imact of the investigated variables in this experiment.