Boron nitride thin films have been prepaied on the (100) surface of silicon substrate by the pulsed ArF excimer laser deposition (PLD) method. The structure and composition of the films have been measured by XRD, FTIR and AES, respectively. The results show that the films are cubic boron nitride (c BN) including small amount of hexagonal boron nitride (h BN). The highest value of Vickers microhardness of the films is about 1580 kg/mm2.