Plasma scalds will be induced in the 1064 nm high reflectivity thin film during laser preconditioning, and they will modulate the laser beam which irradiates the scalds area, leading to laser beam distortion. Energy distribution of 1064 nm continuous laser which irradiates the scalds area is tested, and the reason of modulation and its expression in different laser propagation distance is analysed, both of which provides basis for the functional damage evaluaiton and reasonable use of laser-conditioned sample. The result of the experiment indicates that the pit in the center of scalds may strengthen the peak intensity of beam with annular fringes, and the maximum energy contrast and modulation degree between un-modulated laser beam and modulated laser beam becomes smaller with the laser propagation distance increasing, which means the phenomenon of laser modulation caused by plasma scalds becomes weak with the increasing propagation distance.