Abstract: Site investigation serves as the foundation for environmental management of contaminated sites. However, uncertainties exist across various stages of the investigation process, and there is still no unified definition or technical standard for a precise site investigation. This situation constrains the scientific rigor and accuracy of risk control and remediation decisions to some extent. To address this challenge, this study explores a precision investigation method for contaminated sites based on the multi-source data fusion. Guided by the "pollution source-exposure pathway-receptor" framework, a closed-loop mechanism of "data collection-analysis and evaluation-feedback adjustment" is constructed to integrate multi-source data, including site basic information, hydrogeological data, on-site rapid detection results, in-situ pollution auxiliary detection data, and laboratory test analyses, thereby enabling the dynamic update of the conceptual site model. Meanwhile, a progressive investigation mode of "preliminary sampling layout + in-situ auxiliary pollution detection" is adopted. In accordance with the iterative logic of "pollution scope prediction-detection result verification-sampling scheme optimization", the sampling scheme is dynamically optimized. This method not only achieves the refined characterization of site contamination features and effectively mitigates uncertainties in the investigation process, but also provides theoretical support and practical reference for establishing standardized and normalized technical systems for precision investigation.