在深井、趋深井钻井或修井作业中，套管下入比较困难，环形间隙小、固井质量差，若用无接箍式套管，这些问题便可解决。无接箍式套管靠管体两端的螺纹连接，所以套管外径尺寸小，可增大环形间隙，便于套管下入和提高固井质量。文中介绍了无接箍式套管的分类、结构特征、设计的技术难点、性能和评价方法、主要优点和应用情况。 In deep well, deep well drilling or workover operations, the casing into the more difficult, small annular gap, poor cementing quality, if the coupling without casing, these problems can be solved. The coupling-free bushing is connected with the threaded connection on both ends of the pipe body, so the outer diameter of the bushing is small, which can increase the annular gap, facilitate the casing entering and improve the cementing quality. This paper introduces the classification, structural characteristics, design technical difficulties, performance and evaluation methods, main advantages and applications of the couplingless casing.