In order to investigate the effect of pea )Pisum sativum L.( cultivar and replacement and additive intercropping ratios of pea and spinach )Spinacia oleracea L. (on yield and competition indices, a factorial experiment based on randomized complete block design with three replications was conducted at Gonbad Kavous University research field during 2016-2017. Intercropping ratios at nine levels consisted of pure pea, pure spinach, 33, 50 and 67 percent spinach instead of pea, addition series of 33, 50, 67 and 100 percent spinach to pea and pea cultivars were Shamshiri and Pofaki. Land equivalent ratio and relative crowding coefficient in additive treatments were more than replacement treatments and more than one in all treatments. The highest land equivalent ratio with 1.333 was computed for 100 percent pea+100 percent spinach. In replacement series, pea was as a dominant plant, but in additive series spinach was dominant. No actual yield loss was observed in all treatments. The highest system productivity index was related to 100 percent pea + 100 percent spinach with 3045. Overall, land equivalent ratio over than one and positive system productivity index specially treatment of 100 percent pea+100 percent spinach indicated benefit of intercropping of pea and spinach.