The invention relates to a system and method for generating a safety monitoring self-defined report based on a tree structure, and belongs to the field of safety monitoring of hydropower engineering. The system comprises a data storage module, a data classification processing module, a data retrieval and extraction module, a header generation module and a report generation module; the data storage module, the data classification processing module, the data retrieval and extraction module, the header generation module and the report generation module are connected in sequence; the report generation module is further connected with the data storage module; and the data classification processing module comprises a column grouping classification processing module and a row grouping classification processing module. The method provided by the invention has good reusability, after the method is used, the numbers of measurement points and time points are determined when the report is generated, so when the serial numbers of the measurement points or the number of the time points changes, the template does not need to be changed as the traditional method, and corresponding retrieval conditions are directly increased or decreased, so the workload is small, and the method is easy to popularize and use.