Abstract: In order to lower the well drilling cost, the multi-branch well drilling technique emerged. The multi-branch well drilling technique is a new technique of drilling some branch wells in one well bore and returning to the main well bore. Currently, there are a lot of multi-branch wells drilling methods including the casing pipe opening a window, hammer milling side drill, establishing the window forehand, the naked eye side drilling, the radial branch well drilling method, the inflating tube fixed position side drilling, intelligent branch well, etc. The technique has a lot of advantages including increasing the well bore length in the oil deposit, extending the sluicing oil area, raising the recovery radio, improving the dynamic state section of the oil flows, slowing down taper entering speed, providing the sluicing oil path of the gravity, raising vertical use, raising the crack drilling efficiency, economically exploring the boundary oil reservoir and crude oil reservoir, making use of the upper well segment repeatedly, and lowering the well drilling cost. By reducing onshore and offshore wells it lowers the expenses of constructing platform. It also lowers the expenses of well management and environmental protection, so the economic benefit is raised.