Abstract: The "rice clock". model presented in this paper is dynamic application-oriented simulation model of rice development. It consists of two submodels, i. e. , growth duration model and leaf age model. The former is used simulate the effect of daily temperature and day-length on rice development, with a higher precision and a better explanatory capacity. The parameters of the growth model reflect the basic vegetative duration, thermo-and photo-period-sensitivities for different varietal types. The latter is used to simulate the effect of daily temperature on leaf development. It can estimate the appearance of each leaf blade with different age, and also describe the development and formation of various morphological organs (such as tiller, stem, root and panicle) due to their good synchronizations of growth with leaf development, these two models could be connected well to estimate the number of fully developped leaves in any region and year. Finally, these two modelswere tested and evaluated, based on the experiment data collected from 14 locations (1985), and 8 locations (1986) in the Yangzi River Valley, China,

Key words: Simulation Model, Simulation Model, Rice Development, Leaf Age, Physiological Day