Abstract: A multilateral well is currently the important technology for oil and gas field development. In the process of its research and development, the material selection of branching device plays a key role in the successful application of 6-level multilateral wells in oil and gas fields. According to the twice elastic slope criteria stipulated in ASME Boiler and Pressure Vessel Code, the bursting failure and structural instability of the branching devices in 6-level multilateral wells which are made of IF steel, 10CrMnMoSi dual-phase steel or 2205 dual-phase stainless steel were investigated by using the finite element software Marc. It is shown that both 10CrMnMoSi dual-phase steel and 2205 dual-phase stainless steel can satisfy the design and manufacturing requirements of branching devices, but IF steel cannot meet the compression requirements of branching devices in 6-level multilateral wells. And finally, the reliability of simulation results was verified by performing compression experiments. It is necessary to select material with high strength and plasticity for the design and preparation of branching devices in 6-level multilateral wells.