The invention relates to the technical field of electromagnetic environment analysis. The invention discloses a site electromagnetic environment signal real time analysis and threat evaluation method. The method comprises specific steps as follows: step 1, constructing a signal characteristic database according to the characteristic parameters of various signals, wherein the signal characteristic database is of automatic study manner and can be constantly completed and expanded; step 2, collecting site electromagnetic environment signals, processing the signals to obtain four basic parameters: frequency, bandwidth, power and duration time of the signals, inputting the basic parameters to the signal characteristic database, matching the basic parameters in the signal characteristic database to obtain the modulation styles and types of the signals; step 3, judging the threat degrees of the signals in specific application scenes by a signal threat degree evaluation model according to application scene information, user customized requirements and the signal searching matching results of the step 3. According to the invention, the modulation styles and types of the signals are automatically analyzed through constructing the characteristic database; and then the threat degrees of the signals are judged.