The invention discloses an integrated mixer of a gas engine. The integrated mixer comprises a mixer body, an upper gas rail, a gas inlet connector and a spray nozzle assembly. The mixer body comprises a mixing device and a lower gas rail which are integrated together. The mixing device is tubular. One end of the tubular mixing device serves as the air inlet end. The other end of the tubular mixing device serves as the mixed gas outlet end and is provided with a first natural gas inlet. The mixed gas outlet end is provided with a mixing device core. The lower gas rail is tubular and is integrated on the side face of the tubular mixing device. The outlet end of the lower gas rail is communicated with the first natural gas inlet. The spray nozzle assembly comprises spray metering valves and anti-thrust rubber sleeves. The integrated mixer is high in integration level and convenient to arrange, so that the gas engine is arranged easily, the appearance of the whole engine is attractive, and seal leakage potential hazards are reduced.