The present invention discloses a gas constant-temperature control device. The gas constant-temperature control device is applied to a gas compressor heat exchange system. The gas constant-temperaturecontrol device comprises a gas throttling valve installed in a compressor; the gas constant-temperature control device further comprises a heat exchange pipe for transferring a gas and a spraying head for spraying water mist to the heat exchange pipe; the heat exchange pipe is communicated with the gas throttling valve; the heat exchange pipe is provided with a temperature adjustment portion corresponding to the spatial geometric shape of the water mist sprayed by the spraying head; the temperature adjustment portion is a hollow cone structure which is formed by helically coiling the heat exchange pipe; the spraying head is arranged at the cone tip of the cone of the temperature adjustment portion; and the spraying head sprays water mist to the temperature adjustment portion so as to perform working condition-varying temperature adjustment on the gas in the heat exchange pipe. The invention also discloses a mixed gas throttling system equipped with the gas constant-temperature controldevice. With the system adopted, the temperature of a mixed gas can be accurately adjusted, and the reuse of the mixed gas can be facilitated.