The invention discloses a source tracing method based on light digital quantity value transmission. The source tracing method comprises the steps that a simulation module simulates different signal sources to be transmitted to a light digital source data processing module; the light digital source data processing module inputs the processed light digital signals to a protocol conversion unit so asto generate signal quantity meeting the national standard; the light digital signals converted by the protocol conversion unit are inputted to a standard light digital table data processing module and a light digital table to be measured; and the value error of the standard light digital table data processing module and the light digital table to be measured is calculated by a value error calculation module, and finally the source tracing reliability of light digital quantity value transmission is judged through comparison with the national standard error parameter. The problem of value source tracing of the digital relay protection test device can be solved so that new breakthrough of the digital quantity source tracing technology can be theoretically and practically realized.