Among the atmospheric effect of laser propagation, the variations of the radiation transmittance by water aerosol evaporation have quantitatively been investigated. When the aerosol was exposed by a 1.07 ${mu}m$ cw fiber laser, the increased amount of the transmittance variation was a maximum of 19.1% and the volume concentration variation of aerosol was observed as an increasing of laser intensity. Also, significant irregularity of refractive index was not found in the heated area during the continuous laser heating.