Hexagonal AIN films have been obtained by arc ion plating at different negative biases. X-ray diffraction and scanningelectron microscopy results show that AIN films with smooth surfaces and (002) preferred orientation are obtainedat Iow biases, whereas those with coarse surfaces and (100) preferred orientation are obtained at high biases. Theformation mechanism of AIN is analyzed and the experiment results are discussed. The effect of bias on adhesionstrength has also been examined.