Abstract: Based on the relationship between the concentration and the negative pressure of gas drainage drilling, aiming to the phenomenon of gas emptying and safety hazards because of the low concentration in the gas extraction process, designed a gas concentration adjust valve controlled by the microcontroller that can automatically regulating the gas extraction concentration by adjusting the drainage mouth diameter size of the drilling, Study result show that in the same gas flow supply case, the concentration of the drilling has greatly improved after adjusting by control value , in the basis of the concentration of 70%, the highest concentration improves by 98.1%, the proportion improves by 40.1%, in the basis of the concentration of 5%，the highest concentration improves by 32.9%, the proportion improves by 558%, the final concentration is reduce as the base concentration decreases, while the increasing proportion greatly improve as the base concentration decreases.

Key words: gas concentration automatic control, microcontroller technology, negative pressure regulation, concentration adjustment, control valve