Based on the artless thought that the microstructure and size of precursors determine the size of product nanorods, a simple model was proposed for controlling the size of nanorods synthesized in solution. Within this model, nanorods forming via solvent coordination molecular template (SCMT) mechanism could be synthesized with desired size, despite the great difficulty in exploring crystallization in solvothermal processes. In special, the reciprocal of the nanorods' mean length is in linear relation with the reaction solution's composition, and the length distribution could be predicted by simulation. Our results are in excellent quantitative agreement with the experiments and may provide useful ideas for controlling the size of nanorods forming via similar processes. (c) 2005 Elsevier B.V. All rights reserved.