Abstract: It is important to obtain the real-time atmospheric transmittance of laser waveband with the application of laser technology in numerous scientific fields. Based on measurements and researches of analysis on analogy calculation, a methodology making use of the measurements of sun-photometer to obtain the atmospheric transmittance of infrared laser was proposed. The method was low-cost, high effective, and simultaneous for multiple laser wavebands. Compared with the measurements by 532 nm lidar, the transmittance error is less than 5%. The statistical errors of two infrared laser wavebands are less than 8.5% and 8% respectively, compared with the calculated results by use of the laser transmittance evaluation software based on the real-time measurements of the atmospheric parameters. This method is valuable for the applications of laser engineering in the real atmosphere.