Abstract: In order to measure gas pressure accurately in coal seam and designed borehole parameters quickly and efficiently, established a geometric model for calculating borehole parameters based on the two relative positions between piezometric drilling site and coal seam. According to the spatial relationship among drilling field, drilling hole and coal seam in the model, the formulas for calculating related parameters of upward drilling hole and downward drilling hole are obtained. A numerical example is analyzed by using mathematical software, and the appropriate parameter space for drilling design is obtained. Using the calculation model to designed and constructed the pressure measurement boreholes, it can be find that the error between theoretical calculation length and actual drilling length is less than 10%, which verifies the applicability and accuracy of the calculation formula.