Abstract: The mechanical properties and micro-friction behavior of swine tooth were investigated after various drying treatments, using Vicker's indentation test machine and nano-hardness/scratch tester. Moreover, the recovery of swine tooth's mechanical properties in water was investigated by immersing the dried enamel specimens in deionized water. The objective of this study is to explore the effect of water on biological hard tissue. The results show that the hardness and friction coefficient of swine tooth enamel were associated with its water content. The surface hardness of swine tooth enamel increased with the reduction of water, but the friction coefficient of swine tooth enamel decreased, and they were recovered significantly after water-immersing treatment.