Plaster disruption is recognized as a mural "cancer", and its primary repair method involves grouting reinforcement. Due to the unique nature of cultural relics, directly detecting the reinforcement range of grouting is challenging. To comprehend the spreading range and pattern of the slurry in plaster disruption-damaged layers, an indoor grouting test was conducted using acrylic resin Paraloid B72 as the reinforcing agent. The penetration and diffusion of the slurry within the plaster disruption-damaged layer was focused on, examining the influence of factors such as slurry concentration, porosity of the damaged layer, and grouting methods on the spreading behavior of the slurry. The findings indicate that the trends of injection volume and diffusion range for both vertical and inclined grouting in the damaged layer are similar over time, with no significant differences observed. The diffusion pattern of the slurry is primarily characterized by spherical outward spreading. The spreading range of the slurry increases with larger pore sizes and decreases with higher slurry concentrations. Upon completion of the test, the diffusion range of the specimen was measured to be between 0.65 and 50 cm², with horizontal diffusion distances ranging from 1 to 5 cm and vertical diffusion distances from 1.15 to 10 cm. By utilizing a two-polynomial fit to model the relationship between the diffusion area, penetration rate of the slurry, time, porosity, and concentration, it becomes possible to estimate the diffusion area and the required amount of slurry when the concentration of the slurry and the degree of plaster disruption in the mural layer are known.