The embodiment of the utility model provides a fuel gas supply device and an energy system, relates to the technical field of heat energy, and aims to solve the technical problem of poor utilization of heat energy in the prior art. The fuel gas supply device is used for providing fuel gas for a fuel gas engine and comprises a gas supply pipeline, a gas supply pipeline, a gas supply pipeline and agas supply pipeline, The pressure reducing valve is arranged between the supply port and the air outlet of the air supply pipeline; The heating assembly is used for heating the heat exchange part of the air supply pipeline; The heat exchange part is a pipe body, located between the supply port and the pressure reducing valve, of the air supply pipeline. According to the fuel gas supply system, theexhaust temperature of fuel gas can be effectively increased, so that the density of the fuel gas can be effectively reduced, and the economical efficiency of a fuel gas engine is improved; In addition, the hot water yield can be effectively increased through the fuel gas supply system.