Based on the stellar broad-spectrum imaging signal intensities measured by observational stars day and night, firstly, the calibration error of atmospheric transmittance by Langley method were studied using MODTRAN software. The system parameters and the spectral characteristics of stellar spectra were taken into account during this process. Wide spectral transmittance of the whole atmosphere was obtained by calibrating the intensity of the star imaging. Then, the relationship between the atmospheric transmittance of wide spectrum and the atmospheric transmittance of the laser band was studied by using the atmospheric model, and the atmospheric transmittance of 532 nm and 1 064 nm were obtained. Finally, the atmospheric transmittance measured by stellar observation during the daytime was compared with the solar transmittance measured by the solar radiometer. The results show that the atmospheric transmittance obtained by the two methods has the same trend and the similar size. On this basis, the continuous observation of total atmospheric transmittance is carried out, the diurnal continuous data of total atmospheric transmittance is obtained, especially the data of total atmospheric transmittance at weak turbulence moment of dawn and dusk. The work enriches the measurement of total atmospheric transmittance and promoted the research and application of ground-based laser engineering.