[Objective] The present study developed a system dynamics model to simulate the growth and water use processes of Eucalyptus in order to provide scientific support for the Eucalyptus plantation and management.[Methods] Two frameworks were coupled together by combining the calculation of leaf and root biomass with the simulation of plant water use. Two areas, the Tumbarumba site in Australia and the Jijia forestry farm in Guangdong Province, were selected to test the performance of the coupled model.[Results] In the Tumbarumba site:① The annual average evapotranspiration from the model simulation during 2001-2014 was 819 mm, while the average annual evapotranspiration from the measurements was 867 mm. ② The simulation accuracy of four parameters of chest height diameter, forest volume, tree height and plant density were 71%, 93%, 88% and 95%, respectively. In the Jijia forestry farm:① The evapotranspiration from the model simulation from October 1999 to September 2000 was 1 068 mm, while the evapotranspiration was 1 069 mm. ② The simulation accuracy of four parameters of chest height diameter, forest volume, tree height and plant density were:94%, 89%, 95% and 99%, respectively.[Conclusion] The model can simulate the growth and water use of Eucalyptus, and further improvements especially in the robustness of model are needed.