Abstract: A pipe-in-pipe fast installation structure comprises: an outer pipe; a pliable inner pipe, disposed in the outer pipe; a connector, connected to the outer pipe; and a C ring, formed integrally with an end of the connector. Wherein, the pliable inner pipe penetrates through the outer pipe to extend out from the connector, while an end of the pliable inner pipe is fastened into the C ring. The C ring used for fixing the pliable inner pipe is formed integrally with the connector. As such, the pliable inner pipe can be fastened into the C ring of the connector by making use of the radial compressibility of the pliable inner pipe. The inner pipe and the outer pipe are fixed together through using a special design connector. Therefore, the installation structure is simple in structure, low in production cost, and fast in installation.