A monthly investigation of methane flux in Phragmites australis wetland, Saline seepweed wetland, and mudflat at Liaohe Estuary was carried out from June to November in 2016, using an enclosed chamber technique. Simultaneously, environmental factors, including soil temperature, redox potential (Eh), electrical conductivity (EC), and pH values were measured to evaluate its influence on methane emission. The results showed that:(i) the methane flux in the three types of wetland showed obvious seasonal variations, which is higher in summer than that in spring and autumn; (ii) the methane flux was 0.447-10.40 mg m^-2 h^-1 with a mean of 3.699 ±3.679 in P. australis wetland. During ebb tides, methane flux was 0.045-0.509 and 0.016-0.593 mg m^-2 h^-1 with a mean of 0.165 ±0.156 and 0.198 ±0.191 mg m^-2 h^-1 in the Saline seepweed wetland and mudflat, respectively. The methane flux was significantly different among the three wetland types (P < 0.01), which is highest in P. australis, and followed by mudflat, Saline seepweed wetland; (iii) during flood tide, the methane flux ranged from 0.009 to 0.353 mg m^-2 h^-1 and 0.018 to 0.335 mg m^-2 h^-1 with means of 0.119 ±0.132 and 0.131 ±0.103 mg m^-2 h^-1 in Saline seepweed wetland and mudflat, respectively. The mean fluxes of methane during flood tides were significantly lower than that of ebb tide (P < 0.01); and (iv) furthermore, methane fluxes negatively correlated with the EC values in the three wetland types (P < 0.01). The results indicate that tide and salinity are the key factors to influence methane emission from the coastal wetlands of Liaohe estuary.