Greenhouse experiments in a completely randomized design were carried out to investigate the effects of nitroxin fertilizer (0, 1 and 2 li/ha) on morphological and physiological traits of Amaranthus retroflexus in 2013. The traits in the study included plant height, fresh and dry weight of shoots, roots, stem and leaf, Chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, anthocyanin, and flavonoids. Findings showed that nitroxin biofertilizer had linear and nonlinear regression effect on the fresh and dry weights of shoot. Increase in nitroxin also increased fresh and dry weights of leaf, stem, chlorophylls a, b, total Carotenoids and anthocyanin as well as carotenoids content of the plants linearly. The results showed that the correlation between the traits there is a significant relationship. Also fresh weights shoot with each of traits dry weights shoot, fresh and dry weights of leaf, fresh and dry weights of stem and dry weights of shoot with each of traits fresh and dry weights of leaf, fresh and dry weights of stem and fresh weights of leaf with each of traits fresh and dry weights of stem, dry weights of leaf and dry weights of stem with each of traits dry weights of leaf and stem there is a significant relationship. Chlorophyll a with chlorophyll b, total, carotenoids and flavonoids and chlorophyll b whit chlorophyll total, carotenoids and flavonoids and chlorophyll total whit carotenoids and flavonoids and carotenoids with flavonoids there is a significant relationship. The results of step-wise regression analysis showed that dry weight of stem, had positive and fresh weight of shoots reduced effect on dry weight of shoots.