Abstract: Under controlled conditions in growth chamber, this paper studied the mortality of pepper seedlings caused by Phytophthora capsici. The results showed that soil temperature and water content were the important factors affecting the infection of P. capsici, and their optimum values for the infection were 22-28 ℃ and 40%, respectively. The relationships of the mortality of pepper seedlings caused by Phytophthora capsici with soil temperature, water content and their interactions could be described by mathematical models. Field observation suggested that Gompertz model was the best one for describing the epidemic dynamics of the disease, and the incidence of P. capsici was significantly related to the initial incidence of P. capsici, soil temperature, soil water content, and air temperature. The forecast model of P. capsici incidence on field pepper was established.