A method for updating an object detecting system to detect objects with untrained classes in real-time is provided. The method includes steps of: (a) the object detecting system, if at least one input image is acquired, instructing a recognizer included therein to generate a specific feature map, and to generate a specific query vector; (b) the object detecting system instructing a similarity determining unit (i) to compare the specific query vector to data vectors, to thereby calculate each of first similarity scores between the specific query vector and each of the data vectors, and (ii) to add a specific partial image to an unknown image DB, if a specific first similarity score is smaller than a first threshold value; (c) the object detecting system, if specific class information is acquired, instructing a short-term update unit to generate a specific short-term update vector, and update the feature fingerprint DB.