Two dimensional metal sub-wavelength hole array applicable to THz band (0.1～4 THz) has been made by using femtosecond laser pulses at 775 nm centre wavelength, 1 kHz repetition rate and 130 fs pulse width micromachining copper sheets with thickness up to 300 μm. The diameters of processed hole have been measured as a function of the laser power and the processing time while the processing time and the laser power are fixed respectively. The polarization of the laser radiation is the main cause of the ablation gaps. By using numerical computer simulation technology (CST), the suitable metal hole array structure parameters applicable to THz band have been calculated. According to the above experimental results, the appropriate laser parameters have been chosen to fabricate the hole array.