Due to the large-scale and strong perturbation features of salt bodies, it is very difficult to complete a good salt building with the conventional full waveform inversion (FWI) method without low-frequency data and prior information. The direct envelope inversion (DEI) method is quite effective for salt building when seismic data lack low-frequency information. However, in the current DEI studies, the calculation of the envelope field, which needs a nonlinear envelope operator, does not consider the influences of wavefield overlapping, and the inversion quality of subsalt areas needs further improvements. In this paper, we analyze the effects of wavefield overlapping on envelope field calculation and propose a new envelope field calculation method based on wavefield decomposition. Then, we propose a wavefield decomposition-based direct envelope inversion (WDDEI) method, in which the gradient is calculated using the new envelope field. To improve the inversion quality of subsalt structures, we propose a structure-guided perturbation decomposition method, which can separate the strong scattering salt information from the DEI results with the help of reverse time migration images. Finally, numerical tests are conducted on a modified SEG/EAGE salt model to demonstrate the effectiveness and the antinoise performance of the proposed method.