The invention relates to a device for remotely detecting hazardous gases on the basis of TeraHertz waves. The device comprises a TeraHertz emission source, a TeraHertz signal receiver, a high-speed time delay module, a sealed gas box, a vacuum pump and a gas valve, wherein TeraHertz waves received by the TeraHertz signal receiver in a vacuum environment is taken as a reference signal; TeraHertz waves received by the TeraHertz signal receiver in an environment that remote hazardous gases are introduced into the sealed gas box from a long-distance vacuum pipeline; the two groups of TeraHertz waves are compared, and then the components and the concentration content ratios of hazardous gases in the sealed gas box can be obtained. The remote hazardous gases can be detected by using the TeraHertz waves; the influence that in a common method, light waves can be absorbed by moisture in the atmosphere when probe laser is remotely transmitted in the atmosphere can be avoided; the hazardous gases can be absorbed into the sealed gas box for detection through the long-distance vacuum pipeline, then possible danger of the hazardous gases in the detection process can be reduced, and the device is high in resolution ratio, simple in structure, easy to operate and wide in application range.