Objectives The effects of environmental factors on the early growth traits of alpine Merino lambs were studied to improve the production performance and economic benefits by regulating environmental factors. Methods The lambing records of three alpine Merino sheep herds from 2021 to 2023 were used to analyze the effects of environmental factors including sex, birth type, year of birth, month of birth, and the type of herd on the birth weight of alpine Merino lambs with the general linear model of SPSS. Results The birth weight of male lambs had a significant advantage. The birth weight of single lambs was significantly higher than that of double lambs. The birth weight of lambs born in 2021 and 2022 was significantly higher than that of lambs born in 2023, while there was no significant difference between the birth weight of lambs born 2021 and 2022. The average temperature difference between the months of birth in April and May was 6 ℃, which had a certain impact on the birth weight of lambs. At the level of herd, the birth weight of lambs in the second herd and the third herd was significantly higher than that in the first herd, while there was no significant difference in birth weight between lambs in the second herd and the third herd. Conclusions The effect of environmental factors on the birth weight of alpine Merino lambs was significant, with birth type having the greatest impact. Therefore, it should be given attention in the work of practical breeding.