Methane is one of the most important greenhouse gases and is emitted from waterlogged rice regions. Eddy covariance was used to obtain long-term (2017-2018), high-frequency data for the CH 4 flux at typical rice paddy fields in Sanjiang Plain and Liaohe Plain. This study examines the CH 4 emission process, emission characteristics at different time scales and the intensity of different emission sources. The relationships between CH 4 emissions and temperature and photosynthetically active radiation were also analysed. CH 4 emissions from Sanjiang Plain and Liaohe Plain in 2017 were 26.77 and 16.17 g CH 4 m −2 year −1 , respectively. The CH 4 fluxes in 2017 and 2018 were similar; emissions were higher at the Sanjiang site in 2018. Peak CH 4 emissions (daily average: 0.127 μmol CH 4 m −2 s −1 ) corresponded to the tillering stage in Sanjiang Plain. CH 4 emissions peaks corresponding to the jointing-heading and mature stages at Liaohe Plain. Monthly CH 4 emissions were highest in July. The daily averaged flux was 0.065 μmol CH 4 m −2 s −1 during the growing season. The field-transplanting stage exhibited the highest CH 4 emissions. No CH 4 was emitted during the greening-tillering stages. Emissions increased again during the jointing-heading stages to 0.102 μmol CH 4 m −2 s −1 , and then decreased gradually. A significant linear correlation was observed between PAR and the methane flux in Liaohe Plain. CH 4 emissions in Sanjiang Plain were more sensitive to changes in temperature. The temperature coefficient value was highest from the sowing period to the green period. The CH 4 flux at Sanjiang Plain depended on the stage of rice growth, the temperature, the degree of irrigation and drainage, and the soil pH. In November (during the non-growing season) at Liaohe Plain, a slight negative flux (a weak CH 4 sink) was observed. CH 4 emissions were also found to be inhibited in the growing season by increased soil alkalinity.