In water well drilling， the problems of hole collapse， falling stones， wellbore shrinkage and leakage are prone to happen due to poor stability of bedrock complexity，which seriously affect the quality and efficiency of well drilling. The expandable tubular is an effective measure to solve the wall protection problems in complex formation， but the conventional one is not suitable for water well drilling for its high cost and complex process. In view of this， research was carried out on packer-activated expandable tubulars. The packer is used as the expansion mechanism to make the thin-walled metal pipe expand in the target layer and stick to the well wall， so as to achieve the purposes of wall protection， plugging and casing repair. This paper introduces the development and operation of the expandable tubular system， and the field test of the technology for wall protection and casing repair， which is the first application of the technology in the field of water well drilling and completion.