Sperm freezing is the process of temporarily stopping the life activities of cells without turning off the function of a cell, its metabolic reactions stop approaching totally. The usual semen used for insemination is frozen semen and liquid semen. Frozen semen has a longer shelf life than with liquid semen. The principle of freezing semen is to maintain the survival of sperm in the long term (long term preservation). Thawing is the process of re-melting frozen cow semen before it is used for the Artificial Insemination (IB) process. The temperature and length of time this thawing has a big control on the state of spermatozoa, especially the integrity of spermatozoa in semen. Choose a good temperature and longtime thawing and can properly prevent damage to spermatozoa. The purpose of this study was to analyze the effect of differences in temperature and the length of post thawing time on the viability of FH (Frisian Holstein) cow spermatozoa and to find the optimal temperature and length of thawing time in the IB process. The research method was experimental using RAK with 3 treatment groups and 2x replications. The research material used frozen semen of FH cattle from the Singosari Center for Artificial Insemination (BBIB). The observed variable was Viability with Eosin staining of 2%. Data analysis used the Factorial ANOVA test. The results of this study are the length of time thawing did not differ significantly namely P> 0.05, temperature 25 ° C 20 seconds: 66.30%, 25 ° C 30 seconds: 66.80%, 25 ° C 40 seconds: 63, 30%, 37 ° C 20 seconds: 65.00%, 37 ° C 30 seconds: 74.30%, 37 ° C 40 seconds: 69.00%, 40 ° C 20 seconds: 75.50%, 40 ° C 30 seconds: 65.50%, 40 ° C 40 seconds: 67.50%, the highest percentage of life (viability) of spermatozoa is at 40⁰C with a duration of 20 seconds with a value of 75.50%. Conclusions the higher temperature with the short thawing time can support the high viability. Keyword: Frozen semen, Thawing , Viability, Spermatozoa