The invention discloses a device for preparing natural gas by coupling solar and/ or wind powered generation hydrogen production and coal based natural gas technologies and application. The device comprises a solar and/ or wind powered generation unit, an electricity storing and adjusting unit, an electrolyzing water-to-hydrogen unit, a hydrogen storing tank, a gas mixing tank, a desulfuration unit and a methanation unit which are sequentially connected, wherein the gas mixing tank is connected to a coal based natural gas low-temperature methanol cleaning unit. A method for preparing natural gas through the device comprises the following steps: intermittently and/ or continuously generating power through the solar and/ or wind powered generation unit; electrolyzing water to obtain H2 through the electrolyzing water-to-hydrogen unit; mixing with purge gas of CO2 in H2S removing of the low-temperature methanol cleaning unit in the coal-based natural gas technology; performing desulfuration through the desulfuration unit; then entering the methanation unit to react; processing through a compressing unit; then processing by a decarbonizing unit; and finally mixing with the gas producedby the coal-based natural gas technology, and outputting. With the adoption of the device, the coal-based natural gas yield is effectively increased, and the output of carbon dioxide is decreased.