Abstract: Distribution network line loss rate is a core indicator for measuring grid operational efficiency. Traditional line loss management faces prominent issues such as heterogeneous data sources, inconsistent acquisition cycles, and poor spatiotemporal synchronization. This paper proposes a precise perception method for distribution network line loss based on full-domain data synchronization. By establishing a spatiotemporal alignment mechanism for multi-source heterogeneous data, millisecond-level synchronization of data from marketing, production, and dispatching systems is achieved. A hierarchical and zoned line loss calculation model is designed, establishing a three-level loss tracing system for transformer districts, feeders, and substations. A six-month application verification was conducted in a 10 kV distribution network of a prefecture-level city. The line loss calculation accuracy improved to 98.7%, and the identification accuracy of abnormal transformer districts reached 95.3%, representing improvements of 12.4% and 18.6% respectively compared to traditional methods.