Abstract: Abstract: In order to explore the application effect of PBAT/PLA fully biodegradable mulch on Xinjiang cotton, this study selected PBAT/PLA fully biodegradable mulching film as the research object, compared with PE mulching film, carried out PBAT/PLA fully biodegradable mulching film application test in Shihezi reclamation area, investigated the degradation performance change of PBAT/PLA mulching film, and systematically analyzed the degradation performance of PBAT/PLA mulching film and its impact on soil temperature and humidity, cotton growth and yield. The degradation performance of PBAT/PLA mulch and its effects on soil temperature and humidity, cotton growth and yield were systematically analyzed. The results showed that the PE mulch was damaged in different sizes in the field environment, but the characterization test showed that it did not have intrinsic degradation behavior. The degradation rate of PBAT/PLA mulch was fast, and it entered the induction period after covering for 43 days, and from covering for 136 days to cotton harvest, the film was in the fragmentation period. Fourier transform infrared spectroscopy showed that after degradation, PBAT/PLA mulch appeared with a new characteristic absorption peak, and the strength of the group characteristic peak increased. The crystal type analysis showed that the original crystalline type of PBAT/PLA mulch had not changed after degradation, but the crystallization capacity was enhanced. At this stage, PBAT/PLA mulch experienced cross-linking and branching of molecular chains, breaking of molecular chains in the amorphous region, and rearrangement and crystallization of short-chain PBAT. The observation of micromorphology also confirmed that PBAT/PLA mulch had good degradability in the soil cultivation environment. With the early cracking of mulch, the full bud stage, flowering stage and boll opening stage of cotton in PBAT/PLA mulch group were 1 d, 3 d, and 3 d later than those in the PE mulch group, respectively. In the early stage of cotton growth, the PBAT/PLA mulch surface remained complete, the effect of increasing temperature and preserving moisture was good, and the seedling emergence rate of the two groups was comparable. However, as the PBAT/PLA mulch gradually cracked, its application effect began to decline. After cotton entered the full bud stage, the soil temperature and water content under PBAT/PLA mulch were 0.30-1.15℃ and 2.31-3.46 percentage points lower than those under PE mulch, respectively. Ultimately, the plant height and stem diameter of the PBAT/PLA mulch group were 22.08% and 12.82% lower than those of the PE mulch group, respectively, and the seed cotton yield was 20.24% lower. Therefore, the biodegradable mulch formula with PBAT/PLA as the main raw material needs to be further improved, especially in terms of the regulation of degradation performance. It is urgent to design the molecular chain structure of the material, postpone its degradation induction stage to match the needs of cotton for temperature increase and moisture preservation, and realize rapid degradation after cotton enters the boll opening stage, so as to hopefully replace PE mulch in the cotton production system in the Shihezi Reclamation Area, Xinjiang. This paper provides a reference for further research and development of biodegradable mulching film suitable for cotton production in Xinjiang.