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Based on the observation data of the open-circuit CH₄ gas analyzer at Shouxian National Climatological Observatory, we analyze the variation characteristics and influencing factors of CH4 flux in different growth periods of rice-wheat rotation farmland in the Huaihe River Basin. The results show that CH₄ flux in the Huaihe River Basin has a single peak distribution throughout the year, with the peak occurring in summer. The diurnal variation of CH₄ flux shows a single peak during the day, and the peaks mostly appear in the afternoon. CH₄ flux during the day is higher than at night. CH₄ flux in the rice growth period is significantly higher than that in the wheat growth period. During the wheat growth period, CH₄ flux is the smallest during the seedling period but the largest during the mature period, reaching 0.14 μg ·m^-2·s^-1. During the rice growth period, the maximum CH₄ flux during the jointing period is 3.02 μg ·m^-2·s^-1, and the minimum during the maturity stage is 0.12 μg ·m^-2·s^-1. CH₄ flux decreases by 50% and 30% before and after the harvest of rice and wheat. This study shows that crop biomass has a significant impact on CH₄ flux. CH₄ flux is positively correlated with precipitation, relative humidity, water vapour pressure, soil temperature, and air temperature. When precipitation, humidity, or air temperature is higher, the CH₄ flux will be greater.