Obtaining real-time laser atmospheric transmittance is crucial for laser technology applications in many scientific fields. Based on measurements and research on simulations, a method using the sun-photometer direct radiation measurements to extract infrared laser atmospheric transmittance is proposed herein. The method is effective, inexpensive, and can be used simultaneously for multiple laser wavebands. Compared with the measurements obtained using a POM02-type sun-photometer, errors of transmittance and precipitable water measured using a homemade ISP-type near-infrared sun-photometer are less than 7%. The 1.315-μm transmittance is extracted from 1.31-μm and 1.32-μm data. The extraction errors proportional to the precipitable water are less than 4% for two sun-photometers. Compared with precipitable water reversed from 0.94-μm data, the extraction error of precipitable water reversed from 1.32-μm data is less than 10%. Therefore, the precipitable water can be reversed from 1.32-μm data when 0.94-μm data is not available. The statistical error of 1.315-μm laser atmospheric transmittance calculated by the proposed method is less than 6% compared with the results calculated using laser transmission evaluation software based on real-time measurements of atmospheric parameters. This method is valuable for laser engineering applications in the real atmosphere.