Abstract: To further study the mechanism of negative pressure and drainage effect to determine the reasonable negative pressure interval and achieve the goal of low consumption and high production of gas drainage, by setting up an experimental platform to simulate the extraction process under different hole lengths and different hole negative pressure conditions, the variation laws of relevant extraction parameters at different hole depths were tested. The results showed that the negative pressure and flow rate in the pipe decreased gradually with the hole length, showing a negative exponential relationship. For the same test site, with the increase of negative pressure in the pump station, the negative pressure and the flow inside the tube also increase, but the increase range decreases gradually. According to the test investigation in No.3 coal seam of a certain mine, with the increase of negative pressure, the extraction concentration and the extraction purity both increase at first and then decrease, and the two parameters and the extraction negative pressure constitute a typical quadratic function relationship, respectively; while the extraction mixing amount increases linearly with the increase of negative pressure, which shows a linear function relationship; the derivative extremum method is used to determine the best gas extraction in No.3 coal seam. The negative pressure range is 30.78 kPa to 34.50 kPa. The research results have important guiding significance for improving the effect of mine gas extraction.