Abstract: When the technology for water prospecting by pulling pipe strings is applied in horizontal wells with long horizontal sections in Changqing Oilfield, it is difficult to control the setting pressure of matched mechanical packers, and the damage of sealing rubber cylinders caused by repeated setting results in a sharp reduction in the stability of packer setting tools. In view of these problems, an electrically controlled packer for horizontal wells was developed, which could bring about setting and unsealing on time or in real time, as well as packing of arbitrary layers. In terms of its design, the packer fully considered the repeated setting times in horizontal well sections and the pressure-bearing performance of seals. In particular, the power output part of the driving mechanism adopted a direct current motor and planetary reducer, and the motion conversion part used a screw and nut pair mechanism, so as to ensure that the output torque was maximized, and the packer rubber cylinder was compressed and set in the allowable casing space. The performance such as temperature and pressure resistance, output torque, and setting thrust of the electrically controlled packer were evaluated by laboratory tests, and the related indexes could meet the design requirements. Field tests were conducted in three wells in Changqing Oilfield. The results showed that the packer can minimize the impact of engineering conditions and improve the success rate and test quality of operations. Furthermore, it makes the technology of water prospecting by pulling pipe strings more convenient and economical.