The dust concentration of flour processing factory if the control is not good, it will not only improve the incidence rate of workers occupation disease, but also can easily cause dust explosion prevention, in order to control the harm, the system uses STC89C52 as the main control chip, combined with the dust concentration sensor and the oxygen concentration sensor, A/D converter, LCD display circuit and the module of warning circuit etc.to realize the dust concentration and oxygen concentration value of the realtime detection and display, and outside a safe range automatically give an alarm signal. Through the analysis of the test data and the error of a small flour milling workshop, show that the system can realtime monitor the dust concentration and oxygen content a relatively confined space . The system is simple and easy to operate, and has a certain practical value.