The invention relates to a silt deposition prevention method. The method comprises the steps of judging an easily silted area where silt is easy to deposit in a water area, and digging a silt prevention facility placement pit on an original mud surface of the easily silted area; selecting a capsule assembly according to the size of the silt prevention facility placement pit; conveying the capsuleassembly to a position above the easily silted area; and filling an accommodating cavity with water through a water filling port of the capsule assembly, so as to make the capsule assembly sink into the silt prevention facility placement pit. Since the height of the capsule assembly after water filling is larger than the depth of the silt prevention facility placement pit, and the top wall of thecapsule assembly is located between the water surface and the original mud surface, so that the water depth of the easily silted area is reduced, and the flow rate is increased. After the flow rate ofthe easily silted area is increased, the silt falling probability of silt in the easily silted area is effectively reduced, meanwhile, the silt starting probability in the easily silted area is increased, the silt carrying capacity of a water body in the easily silted area is increased, and the effect of reducing silt silting in the easily silted area can be achieved. Meanwhile, the method is small in disturbance to the water area, free of pollution, low in cost and capable of being repeatedly used.