Abstract: Dimethylformamide(DMF) was added at volume fractions of 2%，3%，4%，5% and 6% to the diluents instead of glycerol used to freeze boar semen completely. The effect of equilibration time and DMF volume fraction on the quality of cryopreservation of boar semen was assessed in experiment. The results showed that DMF could improve boar sperm quality significantly in frozen-thawed process .The best equilibration time was 90 min，its sperm motility was （44.57±0.72）% after freezing and thawing which was significantly higher than other groups(P＜0.05)．Sperm viability， motility， mitochondrial activity，acrosome integrity and membrane integrity for 5% dimethylformamide of boar sperm after freezing and thawing were （49.91±0.39）%，（46.51±0.26）%，（47.51±0.52）%，（49.84±0.56）% and （46.30±1.61）%，and were superior to 2%，3%，6%DMF(P＜0.05). Compared with 4% DMF， sperm viability， motility and membrane integrity were similar to 5% DMF after freezing and thawing(P＞0.05)．To sum up，DMF could replace glycerol completely，and the volume fraction of 5% DMF showed a better effect on the quality of boar cryopreservation semen.

Key words: boar semen; dimethylformamide; equilibration time; cryopreservation; sperm quality