A 2 year field study was carried out at Agricultural Faculty of Shahid Chamran University of Ahvaz (Iran), in order to evaluate the response of Amaranth cultivars and weed dynamic to N splitting methods. Three Amaranth cultivars (i.e., Amont, Trigin and Plainsman) were grown in three N splitting methods (i.e., Commonly, Equal and Semi-equal) that being applied at planting, 12th leaf appearance and stem elongation. A split plot design replicated three times was used which Amaranth cultivars and N splitting methods were arranged in main and sub plots, respectively. Results showed that the highest forage yield was obtained for Trigin with Equal N splitting (i.e., 31.2 t ha(-1)) and Plainsman with Semi-equal N distribution (i.e., 3.8 t ha(-1)) the lowest. Also, the maximum and minimum protein content (%) were obtained for Trigin with Equal N splitting (16%) and Amont with commonly N splitting (11.9%), respectively. It was found that just Trigin with Equal N splitting treatment was the best treatment for both forage quality and quantity yield. Moreover, the weed communities and dominant species changed in response to various N splitting methods and Amaranth cultivars traits. Plainsman with Semi-equal N splitting treatment was the unfavorable treatment for both crop yield and weed infestation. Based on these results it is recommend that N splitting method be applied mainly as an Equal form in Trigin amaranth cultivar, to enhance crop forage yield and reduce weed infestation.