Cotton bowl worm Helicoverpa armigera Hübner (‎Noctuidae family) is one of the most important and key polyphagous pests in the world that attacked the Pistachio orchards of Iran in the recent years considerably. In this study suitability of 4 different diets formulated based on cowpea, pinto bean, chick pea and all these three diets together was evaluated. The lengths of larval development period were measured 11.880, 12.810, 19.105 and 24.105 days when larvae fed on all three diets together, diets based on cowpea, pinto bean and chick pea respectively. The mean lengths of prepupation periods were determined as 2.348, 2.887, 3.522 and 3.739 days respectively for the mentioned diets. The mean lengths of pupation period were calculated as 11.050, 12.357, 12.250 and 16.667days respectively. The mean adult longevities (without sex separation) were measured to be 19.833, 21.167, 19.267 and 16.933 days and the mean pupal weight were 1.88, 1.77, 1.59 and 1.84 gr, respectively. Furthermore the percentages of adult emergency were 96.346, 43.636, 34.545 and 21.818% respectively when larvae fed on mentioned diets. The mean comparison of biological reactions such as length of larvae, prepupation and pupation periods indicated that all three diets together, diets based on cowpea, pinto bean and chick pea were suitable for this pest respectively and caused a shorten immature stage development period, and there is no significant difference between all three diets together and cowpea. However adult emergence is significantly higher when larvae reared on all three diets compared with cowpea. The Pupal weight decreased significantly when larvae reared on pinto bean but there was no significant different among cowpea, chick pea and all these three diets. As a conclusion all three diets could be suggested for mass rearing of this pest applied in many experiments and some controlling methods.