Abstract: The cable-controlled intelligent separate-layer water injection technology realizes the continuous monitoring and real-time measurement and adjustment of downhole parameters, and provides sufficient data for reservoir analysis. However, due to the application of multidisciplinary downhole tools and the complexity of the technology, it is found in the previous field test that the number of wells with cable-controlled intelligent separate-layer water injection wells operating for more than 2 years accounts for only 51.9% of the total, which cannot meet the requirement of large-scale application. Through the fault analysis of the previous test wells, this paper finds the key factors affecting the process reliability. To solve the main affecting issues found in the fault analysis, the flow control valve of the cable-controlled intelligent water distributor, the cable sealing connection process and the structure of the well-flushing valve of cable-through packer are improved and optimized, and the smooth opening and closing of the flow control valve of the cable controlled intelligent water distributor under the pressure difference of 10 MPa is realized, with the leakage less than 1 m³/d. The connection between the cable and the cable-controlled intelligent water distributor is reliable, and the cable can be feed through smoothly through the upper and lower connectors of the cable-through packer. After the optimization and improvement, by April 2022, this technology has gone through field tests in 223 wells, and the proportion of wells running smoothly for more than 2 years increased from 56.1% to 91.9%.After optimization, the reliability of the cable-controlled intelligent separate-layer water injection process has been improved, laying a foundation for large-scale application of the technology in oilfields.