The invention aims to provide a conveniently maintained methane tank which comprises a tank body and a tank cover. The conveniently maintained methane tank is characterized in that the tank cover is movably erected on two horizontal guide rails and can move along the horizontal guide rails to open or close the tank body, water tanks parallel to the guide rails are arranged on two sides of the top end of the tank body and placed between the two horizontal guide rails, and sealing plates submerged in the water tanks are arranged on two sides of the bottom of the tank cover. Auxiliary water tanks communicated with the water tanks are arranged at two ends of the horizontal guide rails on the tank body, auxiliary sealing plates submerged in the auxiliary water tanks are arranged at the bottom of the end of the tank cover and connected with the sealing plates to form an 'n'-shaped structure, and at least one auxiliary sealing plate is detachably mounted on the tank cover. The tank cover of the conveniently maintained methane tank can quite conveniently and horizontally move, maintenance of the methane tank is quite facilitated, and gas leakage of the methane tank is avoided as a water sealing structure is formed between the tank cover and the tank body.