The scattering theories of molecules and Rayleigh are applied in the analysis of the deference between fog to solid targets. And GaN-based blue-violet laser diodes and infrared diodes are compounded to a dual-wavelength diodes array. The dual-wavelength diode is used to test the deferent scatterings character of the fog. And for this measurement, a phase-locked circuit is also used. The scattering-ratio of the GaN-based blue-violet laser diodes and infrared diodes is more than 3. Therefore, the GaN-based blue-violet laser diodes can be used in anti-interference from fog for laser proximity-fuse. The thicker of the fog density, the effect is more significant.