To improve the accuracy of all-sky cloud detection of ground-based infrared cloud-measuring system, the corresponding relation between downwelling infrared radiation and optical depth of clouds was simulated by Santa Barbara DISTORT Atmospheric Radiative Transfer (SBDART) model. The simulation result shows that it is feasible to invert optical depth by fitting its curve. On this basis, a new method under a combination of infrared and laser technologies was proposed. First, more accurate atmospheric profiles and precipitable water vapor applicable to specific regions and seasons were established. Simultaneously, the aerosol and cloud base height were inverted by laser extinction profiles. Second, the atmospheric parameters obtained above were substituted into SBDART to simulate the cloud optical depth inversion curve at zenith. Finally, the optical depth distribution of the all-sky clouds could be inverted by the curve. The experimental results reveal that the distribution of the all-sky optical depth obtained from the inversion curve of single- and two-layer clouds is consistent with the distribution of the all-sky radiation. Moreover, the optical depth of clouds at different heights in the all-sky is clearly distinguished.