Choking on toys is a common global occurrence. However, since there are no methods to observe the process of airway obstruction during human and animal experiments, clarification of the mechanisms has not been elucidated. To solve this problem, we visualized and analyzed choking on toys using Swallow Vision®, a computer simulator of swallowing behavior. The model of the oral cavity to esophagus was constructed based on CT images of a 9-month-old boy and videofluorography images of a 9-month-old girl. The simulated toy shapes included a sphere, hemisphere, rectangle, disk, and cylinder. The parameters of the toys, such as friction coefficients were measured during the experiments. To simulate the behaviors of organs and toys, the Hamiltonian MPS method, which is a particle method for analyzing the fluid–structure interaction, was applied. Particle methods do not require the generation of a mesh. From the simulation results of 48 toy models of various sizes, shapes, and parameters, it was found that the risks of choking were high when the toys were spherical and 6 to 20 mm in size. Toys less than 6 mm were accidentally swallowed. Depending on the occlusion position, choking could be classified as either laryngeal or pharyngeal obstruction. Regarding the mechanism of the toy’s entry into the pharynx, a toy larger than 10 mm must be transferred to the pharynx by a sudden induction of the swallowing reflex, because the fauces, which is the boundary between the oral cavity and the pharynx, is narrow. On the other hand, in the case of a small toy, aspiration might also be the cause; however, the influence of air flow must be studied in the future.