Abstract: A field experiment with various transmittance of plastic films was conducted to identify the optimum film transmittance for transplanting short tobacco seedlings under plastic film in the western Sichuan Province. The experiment used a randomized complete block design with 4 treatments (100%, 36.39%, 14.36%, and 2.10% transmittance) and 3 replicates. The results showed that the maximum air temperature in the cavern under white film (100% transmittance) was up to 40.7℃, and the survival rate of tobacco seedlings was severely reduced, while the maximum air temperature in the cavity under black film was 35.7℃, and the survival rate of the seedlings was above 98% within 15 days after transplanting. For the treatment with higher transmittance, the seedlings was more likely to develop fast, and had a higher ratio of roots to stem and leaves, resulting in a higher plant height, stem circumference, length of maximum leaves and leaf width. The lower the transmittance, the better the appearance quality, chemical composition content and coordination of tobacco leaves. In conclusion, it is recommended to use black plastic film with a transmittance of 14.36% under the local ecological conditions.