Water security, one of the most important part of socioeconomical, ecological environment and even national security, is closely related to human survival and sustainable social economic development. As a prospective study to the future science and technology innovative development in hydraulic engineering, six major technology issues concerning current water security situation that require focuses in the medium to long term future are proposed based on the Water conservancy strategic development research set up by the Technological Science Division of CAS, which includes (1) water security under global climate change and human activities, (2) efficient utilization of water resources in agriculture, (3) rivers-lakes-coastal sediment and ecological environments, (4) the drive and restriction key factors of hydropower energy development, (5) long-term safety operation of cascade hydropower stations with high dams, (6) flood and drought defense. Based on the national security strategy of water demand, frontier scientific issues of water science and technology were proposed herein aimed to provide impetus and support for the research and development of hydroscience and technology.