Abstract: In order to explore the interaction and competitive coexistence mechanism between pest and natural enemy populations, the dynamic temporal pattern, niche breadth and overlap of pest and natural enemy populations in cotton field were systematically investigated by direct observation. The results showed that dominant species of pest and natural enemy were different in different growth duration of spring cotton. The peak period mostly occurred in June and July. The peak periods of Aphis gossypii Glover and Empoasca biguttula were in late May and late September, respectively. Different populations had distinct temporal niches. For pests, niche breadth of cotton mirids was the largest, followed by Helicoverpa armigera, and Empoasca biguttula and Tetranychus cinnatarinus had relatively smaller niche breadth. For natural enemies, niche breadth of arachnid in cotton field was the largest, followed by Orius minutes, and Scymnus hoffmanni had relatively smaller niche breadth. While Scymnus hoffmanni and other coccinellid species had large niche overlap with Aphis gossypii Glover and Tetranychus cinnatarinus. Thus, it was deduced that coccinellid species could be applied to control Aphis gossypii Glover and Tetranychus cinnatarinus, and natural enemies such as spiders should be protected and exploited. Helicoverpa armigera and cotton mirids should be the key species to be controlled in direct-seeding spring cotton fields in southwest Anhui Province.