The invention relates to a deep-pipe inner wall coating thickness measuring device in order to overcome the defects of the existing measuring device. The deep-pipe inner wall coating thickness measuring device comprises a measuring pressure head, a measuring device, a flexible push rod, a tubular measuring pipe with a scale, a flexible push rod guide protection pipe, a spring, a flexible push rod pressure head, a measurement display device, a measurement data output wire, a sliding support, a measurement guide benchmark, and an airfoil support. The measuring pressure head is installed on the measuring device. The measuring device is connected with the flexible push rod through the sliding support. The flexible push rod, the flexible push rod guide protection pipe, the spring and the flexible push rod pressure head constitute a measurement drive device. The tubular measuring pipe with a scale is provided with a window through which the measuring pressure head can extend out. The measurement guide benchmark is installed on the tubular measuring pipe with a scale. The airfoil support is installed outside the tubular measuring pipe with a scale. The measuring device transmits measurement data to the measurement display device through the measurement data output wire. The deep-pipe inner wall coating thickness measuring device has a simple structure, and the measurement data is accurate and reliable.