Abstract: Multilateral well drilling is a popular and challenging new technology in the 21st century, and one of the most important technologies in oil drilling industry Multilateral wells are highly effective for reservoir development and construction, yet drilling and completion of multilateral wells are complicated. The advantages, its development and TAML (technology advancement of multi-laterals) levels classification are described in this paper. Some key technologies related are discussed from such aspects as recovery enhancement, commercial production, cost reduction and benefits improving, etc. It points out that this technology is still in its early stage in China, and it will be the important and fundamental drilling technology in the future.