Abstract: In order to improve boar sperm quality in frozenthawed process, trehalose was added into the basic extendersTrisCitric acidGlucose. The effects of trehalose on quality of cryopreservation of boar sperm were investigated. Moreover, in order to determine the optimum concentration of trehalose, we designed four different concentrations:25%,50%,75% and 100%(v/v), respectively. The results showed that the effects of the basic extenders supplemented with trehalose on cryoprotection of spermatozoa were better than that of traditional TrisCitric acidGlucose (TCG) without supplement. We found out that TCG extender with 25% trehalose concentration significantly enhanced motility, viability, mitochondrial activity, membrane integrity and acrosome integrity of boar sperm after freezing and thawing（P<0.05）, and they were 41.38％,46.34％,44.56％,43.51％ and 64.09％, respectively. Extender containing 25% trehalose could enable some improvement of cryopreservation of boar semen over the currently used TCG medium. Trehalose could decrease distinctly the percentage of spermatozoa capacitated caused by freezing and thawing(3.68％). Capacitation potential was improved significantly with the addition of trehalose in the diluents, especially at 25% concentration(41.82％). The optimal concentration of glycerol in extender was found to be 2%(v/v). Trehalose could improve spermatozoa quality after freezethaw process when there was glycerol in the extender. The results of present study indicated that there was a significant positive correlation among sperm motility, viability, mitochondrial activity, membrane integrity and acrosome integrity（P<0.01）. However, the percentage of spermatozoa capacitated before capacitation treatment was highly negative correlated with sperm quality index in this study（P<0.05）.