In order to obtain high sperm livability after thawing of frozen boar semen, the different combinations of 1st and 2nd dilution with egg yolk tris-dilutor (E), skim milk dilutor (S) and E+S (1 : 1) were studied, Acrosome system of pre and post-frozen spermatozoa in the dilators of different combination was also studied Fertility of frozen semen in the dilators of different combination was tested. The results obtained from these studies were as follows 1. The semen in first dilator with E+S and second dilator with S showed highest post-thawing livability among the treatments. 2. The semen in 1st dilator with E+S and 2nd dilator with S showed highest livability among four diluents during 7 hrs storage at room temperature after thawing. 3, Sixty to 70% of spermatozoa were injured in acrosomic system especially as a slight injury by freezing of semen. This injury of acrsomic system was somewhat inhibited by 1st dilution with EMS and 2nd dilution with S. 4. None of the two sows inseminated with frozen semen in 1st dilutor with E and 2nd dilutor with E was pregnant, but one of the four sows inseminated with frozen semen in 1st dilutor with E+S and 2nd dilutor with S was pregnant and produced five litters with two female and three male pigs, and another three were not pregnant.