The triangle cross-section carbon fiber reinforced plastics could be used as absorbing composite materials, in which the incident microwave can be reflected many times to be greatly attenuated. The microwave absorbing property is affected significantly by the distribution of the triangle cross-section carbon fibers in the composite materials. In this study, the distribution of the triangle cross-section carbon fibers in the triangle cross-section carbon fiber reinforced plastics is investigated by experimental and theoretical simulations. In order to study the angle arrangement and the homogeneity of the carbon fibers in the composite materials, the cross-section morphology of the samples is observed by the SEM. And a process based on the Monte Carlo Method is established to simulate the distribution of the triangle cross-section carbon fibers in the triangle cross-section carbon fibers reinforced plastics. The simulation results agree with the experimental data, which indicates that the triangle cross-section carbon fibers are arranged in a random in angles and approximately homogeneous distribution. This simulation method could be used to simulate the cross-section morphology of the triangle cross-section carbon fibers reinforced plastics with arbitrary fiber contents.