In view of the influence of aerosol on off-axis laser beam guidance, based on Mie scattering theory, the scattering characteristics of atmospheric molecules and aerosol particles are analyzed, and an off-axis laser detection model is established. By studying the transmission characteristics of 1.064 μm laser in low-altitude atmosphere, the correlation between three aerosol types and phase function, direct radiation and scattered radiation is simulated and analyzed. Results show that aerosol type is an important factor affecting the off-axis laser detection results. Under the influence of aerosol, the maximum attenuation of direct radiation energy is 60%. Under the condition of constant aerosol type, relative humidity and detector, the irradiance intensity in short distance (1 km, 3 km) decreases rapidly, while in long distance (8 km), it can be received by the detector at a further off-axis distance, and the final intensity approaches 1 W/m2. When the off-axis detection angle is different, the smaller scattering angle will propagate to farther off-axis distance, and the larger scattering angle will receive more irradiance energy.