The distribution of the scattering signal's irradiance of 1. 06μm laser in atmosphere is calculated by u-sing Mie's scattering theory. The distribution curve of the irradiance along laser beam is given in the low atmospheric model. Through the analysis, the conclusion is gotten that the distance between the point of the maximal irradiance and the laser is inverse relation with the abaxial distance of the detector and it is difficult to orient the laser by one detector, it should use several detectors.