An experiment was conducted to investigate the effect of irrigation water management practices and rice cultivars (BRRI Dhan -28 and BINA Dhan -8) on methane (CH4) emission and rice productivity during Boro season (January to May 2011) at the experimental field o6f Department of Environmental Science, Bangladesh Agricultural University, Mymensingh . Two different rice varities such as BRRI Dhan-28 and BINA Dhan-8 was selected for the study. Different water management practices such as Continuous flooding (CF) at 5 cm standing water, CF at 5cm standing water for first 3 weeks, CF at 5cm standing water for first 6 weeks, CF at 5cm standing water for first 9 weeks, alternate wetting and drying(irrigated at 5cm depth, 3 day in a week and 4 days drying) and water saturated condition (no standing water) were followed in the different plot in this experiment. It was observed that alternate wetting and drying (irrigated at 5cm depth, 3 day in a week and 4 days drying) treatment gave highest yield 5.76 t/ha and 6.713 t/ha respectively in BRRI Dhan-28 and BINA Dhan-8. However the lowest seasonal methane emission 13.349 g CH4/m2/season (26.37% less than CF at 5 cm standing water) and 13.808 g CH4/m2/season (28.08% less than CF at 5 cm standing water) were found under the alternate wetting and drying in BRRI Dhan-28 and BINA Dhan-8 respectively. So alternate wetting and drying(irrigated at 5cm depth, 3 day in a week and 4 days drying) irrigation water management practice should be followed for reducing CH4 emission and sustaining rice productivity during the Boro season in Bangladesh climatic condition.