The purpose of this study is to evaluate the effects of astaxanthin added to freezing buffer on semen parameters, total sperm oxidation stress after post-thawing of boar sperm and lipid peroxidation (LPO) which is caused by reactive oxygen species (ROS) in sperm membrane. Varying concentrations of astaxanthin (0, 10, 50, 100 and 500 μM) were used in the freezing buffer during cryopreservation to protect the DNA of thawed miniature pig sperm. Semen parameter was measured using computer assisted sperm analysis (CASA) for sperm motility and determine ROS rate, oxidative stress of boar sperm using fluorescence-activated cell sorting (FACS). Sperm motility was higher (p<0.05) in the astaxanthin group than in the control group. Sperm motility and the number of progressive motile sperm was higher (p<0.05) in the astaxanthin 500 μM group (66±1.7%) than in the control group (49.8±4%). In ROS evaluation, the astaxanthin group lowered intracellular O2 and H2O2 in viable sperm. The Yo-Pro-I/HE and PI/H2DCFDA staining as revealed using flow cytometry was lower in astaxanthin groups than in the other groups. As the result, we found that astaxanthin could protect the sperm plasma membrane from free radical and LPO during boar sperm post-thawing.