Abstract: A simulation model of dry matter partition and yield formation based on the accumulated product of thermal effectiveness and PAR (TEP) is designed in this paper in accordance with the relationship between organ vegetation of sweet potato and temperature and radiation and is validated by the experimental data. The results show that the simulated results of shoot dry weight, root dry weight and tuber root dry matter conform to the actually measured values very well. The fit values between the simulated results and actually measured values are separately 0.97, 0.96 and 0.95 (all obviously related to 0.01 levels) and the forecasted relative errors are separately 1.23%, 1.89% and 2.45%. The simulation system uses C++ Builder6.0 to develop an executable model system on Pentium(R) 4 CPU and 512MB memory computer with Windows XP operation system. Compared with the existing vegetation model of field crop, the model created in this paper not only has high forecast accuracy and complete function but also acquires the parameters easily and has strong practicability. The model can forecast the dry matter partition and yield index so as to provide decision-making support for the production management optimization.