To improve the productivity of cotton fields in red soil drylands, it is necessary to study the yield-limiting factors in these regions, and propose appropriate mitigation measures. Straw mulching is an effective method of straw resource utilization, which could effectively promote the sustainable development of agriculture. To enhance our understanding of the appropriate straw mulching amount in red soil drylands, a randomized block design field experiment was carried out in the Science and Technology Park of Jiangxi Agricultural University (115°55'02.040″E, 28°46'04.476″N, original the Agricultural College Test Station). The effects of the following four straw mulch level treatments were examined:0 kg/hm² (S1), 4 375 kg/hm² (S2), 8 750 kg/hm² (S3), and 13 125 kg/hm² (S4). The present study mainly investigated the yield, emergence rate, plant height, and chlorophyll content of cotton, and also soil temperature. The following results were obtained. (1) Straw mulching treatments increased cotton seedling emergence by 21.5%-28.1%. The difference between mulching treatments (S2-S4) and the non-mulching treatment (S1) was significant at P<0.01, although there were no significant differences among the three mulching treatments. (2) Straw mulching treatments affected the main stem growth of cotton at the late stage of growth, with treatment S4 having the best effect. (3) Straw mulching treatments also promoted an increase in chlorophyll content. Chlorophyll content in each growth period increased with an increase in the amount of straw mulching, with treatments S3 and S4 having the best effects. (4) Straw mulching treatments regulated the soil temperature. The soil temperature increased at 08:00 and 20:00, but decreased at 14:00, although the daily temperature range showed only a small variation. The effect of temperature control was weakened gradually in the straw mulching treatments with an increase in soil depth. This effect was highly correlated with daily mean temperature difference and soil depth during the coverage period, and the correlation coefficient reached 0.98 or higher, which aided in predicting the variation in diurnal temperature range of different soil layers. (5) Straw mulching treatments promoted a highly significant (P<0.01) increase in cotton production, with production in treatments S2, S3, and S4 being 11.4%, 35.9%, and 37.7% higher, respectively, than that in the non-mulching treatment (S1). There was also a gradual increase in yield with an increase in the amount of mulching. Collectively, these results indicate that straw mulching can play an important role in improving cotton yield, seedling emergence rate, plant height, and chlorophyll content, and also in regulating soil temperature in red soil drylands. In this regard, straw mulching at 8 750-13 125 kg/hm² was considerably effective, which would not only be conducive to the production of cotton but could also reduce environmental pollution caused by the burning of straw and improve the utilization of straw resources, and is thus worth popularizing in red soil drylands. However, since the present study was only of a short duration, further long-term studies in red soil drylands are required, particularly with regards to the mechanisms underlying the effects of mulching on the growth of cotton.