The design is based on STC89C52 microcontroller design of intelligent temperature and humidity detection system, the hardware part, including the master chip, DHT11 sensor, 1602 LCD display, buttons and alarm. The software part is written in C language. Under the control of the microcontroller, the temperature and humidity sensor will detect the temperature and humidity parameters, through the port to the microcontroller for processing, while the LCD1602 liquid crystal display on realtime display. And the user can set the temperature and humidity through the key circuit of the highest and lowest threshold, once the value of temperature and humidity exceeds the threshold, you can inform the sound and light alarm management. In the end, the design in the Keil environment to complete the preparation of the C language program, and the joint Protues software to complete the simulation, and the circuit board welding, hardware and software debugging, can accurately measure the environment temperature and humidity, and can achieve beyond threshold alarm function.