AlN thin films have been deposited on p-(100) Si and glass substrates by pulsed bias arc ion plating at different negative substrate biases. The crystal orientation, deposition rate and mechanical property of the films were investigated by X-ray diffraction, nanoindenter and UV-VIS spectrophotometer. The results reveal that pulsed bias has a large influence on film preferred orientation, deposition rate and mechanical property. A preferred (110) orientation is observed in the film deposited at a bias of -50V. With the increase of the bias, film deposition rate decreases first sharply then wildly; Film hardness and elastic modulus first increase, then decrease and finally increases. Higher value of film harness obtained at the bias of -50V and -500V relates to the (110) preferred orientation and grain refinement respectively.