Abstract: Through the airflow state analysis of small wind roadway, it took the small wind roadway as the example which was common in coal mine sites, combined with the mine-used wind sensors GFW15 and GFY15 type which were widely used in domestic coal industry, it quantitatively analyzed the errors of current wind speed sensor in the measurement of small wind speed, and the errors caused by gas emission calculation. It pointed out that the characteristics of the accuracy of the results were not enough through wind speed sensor measurement values were applied directly in gas emission calculation. Combined with the sequence variation characteristics of field data and needs of gas emission data analysis accuracy, it proposed piecewise function methods to discriminate the errors among different measurement range caused by the sensor itself, and established the corresponding piecewise functions. Finally, combined with field data to verify the method, it obtained the conclusion that the gas emission calculation was more accurate through the wind speed value determined by the piecewise functions.