Abstract: In order to study the influence of palte beam angle change on the precision of laser methane sensor, taking the concentration of 2.00% standard gas as test gas, we design 18 times of experiments and determine testing error of laser methane sensor under different beam angles. Through data analysis, we find that plate beam angle within the range of 5 ° to 75 °, the determination of laser methane sensor error has a downward trend; the beam angle within the range of 89 ° to 90 °, sensor measuring error has a rising trend; plate beam angle within the range of 75 ° to 80 °, the sensor measurement error is minimum and remains at 0.04%.