The present invention discloses a method for labeling specific cells within living cells or tissues. The method comprises preparing the vectors with genes of photoactivable fluorescent proteins, followed by injecting the vectors containing genes of photoactivable fluorescent proteins together with genes of other fluorescent proteins into living cells or tissues, resulting in biological tissues with traceable systemic expression and irradiating the predetermined areas in living cells or tissues with an activating
light source, thereby enhancing the intensity and duration of the emitted fluorescent after other excitations, thus revealing the targets intended for observation out of the background, so that a target-oriented
image tracing is achieved.