The invention relates to a cable perforation device for preliminary fracture forming of shale bed rock. A sleeve is provided with an independent inner cavity and an independent outer cavity from interior to exterior in the radial direction of the sleeve, wherein the inner cavity and the outer cavity are communicated in the axial direction of the sleeve. A liquid charging and discharging valve comprises a valve body and a chemical thermal reaction device. The valve body is provided with an electrode introducing structure and a liquid charging structure for charging liquid into the inner cavity and the outer cavity. The chemical thermal reaction device is connected with the valve body and located in the outer cavity. An energy releasing device comprises an energy releasing body which is provided with a through hole and an energy releasing hole, the through hole is communicated with the inner cavity, an included angle of 30-120 degrees is formed between the energy releasing hole and the axis of the energy releasing device, and the energy releasing hole is communicated with the through hole. An external electrode is used for connecting electricity to the cable perforation device, and an inner electrode is used for introducing external electricity into the chemical thermal reaction device. The cable perforation device is safe and reliable, industrial waste gas CO2 is used for replacing explosives, chemical materials are saved, and the environmental-friendly value is achieved. Corresponding burst pressure can be correspondingly controlled according to different terrain.