Zn(bdc)(ted)(0.5) was synthesized for methane storage application. The effects of various factors such as the mole ratio of reactants and crystallization time on the methane adsorption capacity were investigated. The methane adsorption capacity of the metal-organic framework (MOF) synthesized under optimized conditions could reach 15.6 mmol/g. A facile and general carbonization strategy was proposed to modify the surface of Zn(bdc)(ted)(0.5) for improving its hydrophobicity performance. Strikingly, the water contact angle of the carbonized sample could reach 144.2 degrees. As a result, the morphology and crystal structure of the carbonized sample remained essentially unchanged after exposure to a 37% relative humidity environment for 5 days. In addition, the methane storage capacity of the thermally modified sample also could reach 15.0 mmol/g, showing the great application potential of this protocol to improve the stability of adsorption capacity in humid environments. The simulation results proved that the water molecules occupied the channels in the framework or even destroyed the TED and BDC linkers and caused the decrease of the methane gravimetric storage performance of Zn(bdc)(ted)(0.5) in a humid environment. Moreover, an amorphous carbon coating, which can exclude water from entering the framework, was observed to cover the surface of the MOFs during the carbonization process.