Abstract: A simulation model of late-sown rice growth and yield formation was built by using the field experimental data in 1989 and 1990. In this model, the biological processes such as photosynthesis, respiration and growth are considered. Photosynthesis is affected by radiation, temperature and leaf area index. Respiration includes growth respiration and maintenance respiration, as well as photo-respiration. Growth is modeled using net assimilation partition, and yield formation using net assimilation accumulation. The result shows that the simulation model gives a good agreement with the observations from field test