Abstract: Clay was encapsulated with iron tin oxide hydroxide［FeSnO(OH)5］ at different encapsulation ratios through a coprecipitation method. Effects of encapsulation ratio on the flame-retardant, tensile and thermal degradation properties of poly(vinyl chloride)(PVC) were evaluated, and the dispersibility of encapsulated clay was investigated. The results indicated that the addition of clay could not enhance the flame retardancy of PVC, and however, the dispersibility of clay in the PVC matrix could be improved at the loading of 10 phr, which led to a maximum mechanical performance of PVC. When the encapsulation ratio was set as 1∶5, PVC compounds achieved optimum flame retardancy and their tensile properties were also improved. The incorporation of encapsulated clay enhanced the char yield of PVC compounds at 800 ℃, reduced the initial decomposition temperature and maximum weight-loss peak temperature in the first stage, and increased the maximum weight-loss temperature in the second stage. These results suggested that the encapsulated clay could promote the thermal decomposition of PVC and make the decomposition products more stable in the first stage.