Single-photon laser ranging technology has gained widespread application across various ranging scenarios due to its high detection sensitivity. To investigate the impact of atmospheric transmission and background radiation parameters on the background noise at the 1064 nm wavelength under the single-photon detection regime, two atmospheric radiative transfer simulation tools, MODTRAN and CART, are used to calculate and compare the atmospheric transmittance and solar radiation parameters under different detection conditions along a horizontal path, and further simulate and analyze their impact on the background noise count rates. It is found that during daytime ranging, the closer to noon, the lower the background noise, which is more conducive to detection. Additionally, when the detection altitude exceeds 3 km, the influence of ground visibility on background noise is essentially negated, and the higher the detection altitude, the lower the background noise. Moreover, in scenarios with high detection altitude and short detection distance, target background radiation should not be neglected. This paper can provide a valuable reference for the background noise levels in the design of airborne single-photon laser long-range ranging systems, particularly under all-weather conditions and various detection scenarios.