Abstract: The current research of scale effect of irrigation water use efficiency was mainly focused at irrigation schemes with surface water resources, and less involved with groundwater irrigation. Based on the water accounting method developed by International Water Management Institute (IWMI), a general framework for analyzing variability of irrigation water use efficiency indices across scales in well-canal combined irrigation were proposed with return water utilization index, taking Shijin irrigation scheme in Hebei province as an example. In the framework, assessment indices developed by IWMI were explored to access irrigation water use efficiency, and five scales, namely irrigation scheme, main canal, branch main canal, branch canal and field scale, were selected according to the management mode of most irrigation areas in China. Data required for water accounting at those scales were mainly obtained from Shijing irrigation area scheme management agency as well as observation experimentation. Generally speaking, five key aspects of scale effect research of irrigation water use efficiency assessment indices, including assessment indices selection, scale division, water accounting, data collection and return water analyzing, were presented in the research, which could provide some references and experiences to the study on the scale effect of water saving in well-canal combined irrigation area in North China.