The enhanced transmission of terahertzs radiation through the metal subwavelength fractal structures is studied by means of the terahertz time domain spectroscopy (THz-TDS). In view of experiment and theory, the physical mechanism of enhanced transmission of THz wave through each level of fractal lines on the copper film is studied. It is found that THz transmission enhancement in low frequency region mainly resulted from the electron resonance in low level lines, and that in high frequecy region mainly resulted from the electron resonance in high level lines. Thus the transmission enhancement can be attributed to the electron resonant radiation in the fractal structure, namely,the localized resonance efficiency of the frqctal structure.