In this study, we aimed to investigate the effect of different amounts of residual plastic film on soil water horizontal diffusion process. By using the horizontal soil column simulation investigation, Six kinds of residual plastic film(0,80,160,320,640 and 1280kg/hm2) were designed with triplicate. The water wetting front transport distance, the accumulative infiltration amount and soil water content were determined, then we could calculate the Boltzmann coefficient and water diffusivity by using iterative method. The results showed that the migration rate of horizontal wetting front, the accumulative infiltration amount and volumetric soil water content gradually declined with the increase of residual plastic film amount. When residual plastic film amount was more than 160 kg/hm2, the migration rate of horizontal wetting front and the accumulative infiltration amount would dramatically reduce. There were extremely significant positive correlation relationship between the amount of residual plastic film and retardation coefficient. When the amount of residual plastic film ranges from 80 kg/hm2to160kg/hm2, increase rate of retardation coefficient reached up to 251.15%. The distance from stronger retardation region to infiltration point was enlarged with increase of residual plastic film. However, Boltzmann coefficient and water diffusivity were gradually declined, driving force of soil matric potential on soil water diffusion and soil water holding ability wore off. The horizontal diffusion process of soil mixed with residual plastic film still conforms to single parameter model of soil water diffusivity. Our results suggest that the residual plastic film as soil pollutant would reduce migration rate of horizontal wetting front, accumulative infiltration amount and soil water diffusivity, the retardation effect of residual film on soil water diffusion will enhance with residual plastic film amount increasing.