The adding valve for large-diameter pressure water pipelines is widely used in the operation and management of water pipelines.For traditional construction technology，the flange is connected to the original pipeline through welding.However，in practice，it sometimes faces problems such as the size mismatch between the adding valve and the original water pipeline （especially the original pipeline installation of the situation of the long years），too large an inclination of the original pipeline，narrow working space and installation difficulties.These make it difficult to ensure the quality of welding，installation，and other construction work.To solve the above problems，investigation and testing were conducted in this study.The construction technology of large-diameter pressure water pipelines with adding valves is successfully innovated through the production of the telescopic variable diameter connecting the original pipeline with adding valves by cutting discarded materials of original pipelines，and the reasonable application of on-site conventional lifting equipment，including truck cranes and chain hoists.This technology has achieved good results in practical application．