Full waveform inversion, as an advancing theory for extracting elastic parameters of real underground media in seismic exploration, has always been a hot and difficult research topic. On the one hand, due to the limitation of computation capacity, the existing method of full-waveform inversion is mainly based on local optimization algorithm.On the other hand, the limitation of the survey design and frequency range of seismic data make it strong non-linearity, which leads to the success of inversion depends on the accuracy of initial model. In this paper, a full-waveform inversion method using reflection energy constraints is proposed. The purpose is to provide a relatively reliable initial model for conventional full-waveform inversion.Firstly, the scattering wave equation is expressed by using reflection ability operator. Two different scattering models are used to illustrate the ability of reflection energy operator to extract reflection information effectively. On this basis, a gradient operator based on reflectivity constrained full-wave inversion method is proposed and its inversion process is established. Finally, the simple depression medal and the complex nappe model are used to verify that the proposed full-wave inversion method based on reflection energy constraints can effectively provide high accuracy initial velocity information.