Influenced by meteorological, soil, planting conditions and so on, crop water requirement is obviously characterized by its spatial-temporal heterogeneity on different scales. As the result of this heterogeneity, the theories and models of crop water requirement were highly scale-dependent. The calculation method of spatial-temporal features of crop water requirement was expounded. Finally, this paper suggests that, based on the experimental data, a new multi-scale crop water requirement estimating model of theoretical basis and wide application should be developed, and the spatial-temporal features of crop water requirement should be analyzed, using the complexity theories such as the fractal theory, the wavelet analysis and the information entropy approach.