Abstract: The fertility test showed that pregnant rate of AI with frozen semen were significantly lower than that of natural mating. One of the reasons might be the sperm plasma membrane was serious injured during freezing. Therefore, the paper studied on sheep spermatozoa during freezing which was protected with egg yolk （EY） and local fine wool sheep was used as the experimental animals. Then low density lipoprotein （LDL） was used in diluents instead of egg yolk to study on the effect of LDL on sperm motility, acrosome intact rate and plasma membrane integrity. The optimal LDL dilution formula was screened to improve sheep semen quality, reduce the damage sperm, and provide theoretical basis for improving fertility of ram sperm after cryopreservation.