Abstract: Monte Carlo imaging simulation is applied to investigate the impact of filter material properties on accurate and robust reconstruction of the high-energy X-ray spectrum based on the attenuated transmission principle. A model of multi-collimating apertures is designed to simulate the process of X-ray passing through filter materials, and an entire attenuation transmission curve is obtained in a single imaging simulation. It is an ill-conditioned problem to obtain the X-ray spectrum from the transmission data. An improved iterative perturbation method is used to reconstruct the spectrum, which considers minimization of the difference between the calculated and the true transmission curves and smoothness of the high-energy spectrum function. The inherent relation between the attenuation characteristic of the filter material and the accurate-and-robust reconstruction of the spectrum is also verified. The results show that the mass attenuation coefficient of the filter material should be monotonically decreasing over the spectrum.