Abstract: Studied influences on quality of frozen semen in the process of producing rate of temperature drop for equilibration on Henan fat-tailed sheep from 100, 150, 200 and 250 mL water bath. Results indicated: ① the temperature drop time was 2.2 to 3.9 h that four kind water baths treated. The rate of temperature drop with 100 mL water baths was fastest, 250 mL water baths was slowest, 200 and 250 mL water baths was a similar in changes.② Optimum rate of temperature drop was 0.73 to 0.74 ℃/min and 0.11 to 0.12 ℃/min from 0 to 30 minute or 30 to 90 minute, respectively. ③ Optimum time of temperature drop for equilibration was 3 h. The cooling striking was least and the sperm quality was best with 250 mL water baths treated. ④ The sperm motility was not difference with 200 and 250 mL water bath treated, but it was significant difference between 250 and 200 mL treated or 150 and 100 mL treated. ⑤ The aberration rate was not difference with 200 and 250 mL water bath treated, it was significant difference between 250 and 200 mL or 150 mL treated. ⑥ The rate of acrosomal intactness was significant difference between 150 and 100 mL or 250 and 200 mL treated.

Key words: semen freezing; rate of temperature drop; sperm motility; aberration rate; rate of acrosomal intactness