This paper introduces the WBE model and reviews applications of the model to ecology. Provided that organisms are of a self-similar fractal-like network and their metabolic process follows laws of mass and energy conservation, and that energy distributes within organisms with least cost, West, Brown and Enquist（1997）proposed a 3/4 scaling relationship between metabolic rate and body size, i.e. the so called WBE model. Thereafter, based on WBE, Brown et al. developed the metabolic theory of ecology (MTE), which incorporated temperature effect on metabolism rate. The WBE and MTE models have been applied to hierarchic ecological systems from individual to biosphere level, and many scaling relationships based on the models have been predicted and confirmed. At individual level, WBE model predicts that the biomass fixed by leaves has a 3/4 scaling relationship with that fixed by root or stem. The annual growth rate of plant vegetative organs (leaf, stem and root) scales isometrically with respect to each other. Annual reproductive biomass of seed plants has a nonlinear logarithmic relationship with the biomass of leaf, root and stem. Growth rate and mortality rate scales as the -1/4-power of body size. At community level, there is a -1/3 scaling relationship between total standing biomass and population density, while annual community growth rate is irrelevant to population density. At ecosystem level, yield per unit area and energy flow rate have no relationship with individual biomass and increases with environmental temperature rising, namely the energetic equivalence rule (EER). Generally speaking, WBE model has been widely applied in physiological ecology, population ecology, community ecology and ecosystem ecology. Even for global change research, WBE model can be used to determine the parameters that can not be measured directly, for example, the estimation of global belowground carbon storage based on the scaling relationship between plant roots and aboveground parts. Up to now, there are still a lot of debate on the WBE and MTE model, generally focusing on the presumptions of the model and the predicted scaling exponents. This paper tries to show the value of the model and also advances several suggestions for future work.