Abstract: Methane is an important greenhouse gas, which is produced and released actively in estuaries and coastal seas. In 2021, we conducted incubation experiments in the oligotrophic waters of Lufeng offshore (August) and the eutrophic waters of Jiulongjiang Estuary (June) to study the potential production of methane. As shown from the results, methane concentration increased by two orders after addition of carbon, nitrogen and methylphosphonate, suggesting the presence of methylphosphonate-dependent methane production in Lufeng offshore. The methylphosphonate, dimethylsulphoniopropionate and trimethylamine-based methane productions were also found in Jiulongjiang Estuary, with the highest methane-increased rate (211.0%) in the methylphosphonate group. Comparing the experiments conducted in the two study sites with same amount of methylphosphonate addition, we found that produced-methane was 22 times in Lufeng offshore as high as in Jiulongjiang Estuary, indicating that the poor-nutrient water may facilitate the methylphosphonate-based methane production.