Abstract: 【Objective】 To study the effects of compound additives on rumen fermentation. 【Methods】 Sixty 6-month-old Altay rams with similar body weight (39.64 ± 2.72) kg and good health were randomly divided into one control group and three compound additive groups (E₁ group, E₂ group and E₃ group), with 15 sheep in each group. The CON group was fed with basic diet, E₁ group was added with 2.2% compound additive I (seabuckthorn leaf powder: ammonium chloride: glutamine = 15:5:2), E₂ group was added with 2.2% compound additive II (seabuckthorn leaf powder: ammonium chloride: guanylacetic acid = 15:5:1), and E₃ group was added with 2.2% compound additive III (seabuckthorn leaf powder: ammonium chloride: glutamine: guanylacetic acid = 15:5:2:1). The pre-trial period was 15 days and the pilot period was 30 days. 【Results】 The results showed that(1) The average daily feed intake of E₁, E₂ and E₃ groups was significantly higher than that of control group (P<0.05 or P<0.01). The ratio of feed to gain in E₁ and E₃ groups was significantly lower than that in control group during the first 15 days (P<0.01). (2) The acetic acid/propionic acid levels in the E₁ group were significantly higher than those in the E₃ group (P<0.05); The concentration of isovaleric acid in E₂ group was significantly higher than that in the control group (P<0.05); There was no significant difference in other rumen fermentation parameters between groups. (3) The E₁ group had the highest apparent digestibility of dry matter, organic matter, crude protein, neutral detergent fiber, acidic detergent fiber, and total energy, which was significantly higher than those of the control group (P<0.01). The E₂ group had the highest apparent digestibility of crude fat, which was significantly higher than that of the control group (P<0.01). 【Conclusion】 It can be seen that adding composite additives to the diet helps improve the apparent nutrient digestibility of cold season sheep. In summary, the application effect of composite additive I (seabuckthorn leaf powder: ammonium chloride: glutamine=15:5:2) in cold season sheep production is good.