The invention relates to a signal lossless joint and intercommunicating system which is composed of a signal interface layer, a middle transfer layer and a module layer. The signal interface layer comprises a bearing bottom board, and an outer interface and an interface fixing clamp are fixed to the bearing bottom board. A printed board of the middle transfer layer comprises an inner interconnection interface and a signal transmission circuit. The module layer comprises a guide rail frame and a plurality of function modules. The printed board is arranged on the bearing bottom board, and the guide rail frame is fixed to the bearing bottom board. The function modules are matched with the guide rail frame through rail grooves, the function modules are inserted into the guide rail frame, and the circuit connection of the function modules and the middle transfer layer is achieved. Signals are classified layer by layer, short-distance lossless transmission is carried out on the signals, the line arrangement and the distribution of the signals are optimized, and therefore high-speed digital signals, analog signals and radio frequency signals are made to strictly meet linear conditions in the process of transmission between layers, then the lossless connection of the signals between the layers is guaranteed, and the lossless transmission of the signals from an input end to an output end is achieved.