The utility model discloses a gamma ray gas detector, comprising a detecting body, a chamber of a preamplifier and the preamplifier. The preamplifier is arranged in the chamber of the preamplifier. The utility model is characterized in that the gamma ray gas detector also comprises a vacuum humid room. The detecting body is hermetically arranged in the vacuum humid room. The preamplifier chamber is fixedly connected on one side of the humid room. The gamma ray gas detector can thoroughly solve the influence caused by the temperature change of the environment to the stability of the detector, increasing the long-term stability and accuracy of the nuclear scale.