The application of water-fertilizer integration and intelligent irrigation systems in cotton production will greatly promote the increase of cotton yield and quality, which has significant application value for cotton production. This paper introduces Internet of Things (IoT) technology in the water-fertilizer integration and intelligent irrigation system and shifts cotton production to an information-centered production mode. In this paper, water-fertilizer integration adopts the first part of the main pipe fertilizer premixing system, which combines venturi and centrifugal pumps to form a fertilizer mixing equipment and uses sensors to collect the environmental information of cotton growth and development and the growth condition of cotton and also designs the fuzzy PID automation control module to realize water-fertilizer integration and smart irrigation. In the application test on June 22, 2022, the air temperature decreased, humidity increased, and light intensity gradually decreased after 15:30 due to the weather turning cloudy. After the rain stopped around 20:00, the sensors detected that the air temperature reached the lowest value of the test practice section, 28°C, which is sensitive to the environment. Compared with the artificial irrigation method, it can increase cotton yield by 66.98% while saving water by 11.59%, and the application found that the EC value of the fertilizer solution in the fertilizer mixing bucket reached a steady state at about 150s, and the fertilizer decision-making model also has a greater superiority compared with manual.