In order to find a simple and effective method to optimize the process parameter of precursor infiltration and pyrolysis (PIP) process for ceramic matrix composites, the viewpoint of characterization of the mechanical properties of 2D composites using multifilament composites was put forward. Multifilament and 2D SiCf/SiC composites were fabricated by five kinds of PIP processes, and the change rules of mechanical properties of the two kinds of composites with different PIP processes were investigated. Meanwhile, the validity of using multifilament composites to characterize the mechanical properties of 2D composites was analyzed. The results show that the change rules of mechanical properties of multifilament composites with PIP process parameters are in good agreement with that of 2D composites, because their interfaces, fiber damage and other characteristics are basically the same. The ratio of mechanical properties was employed to characterize the consistency between multifilament and 2D composites. The results indicate that the mechanical properties of those two kinds of composites have higher consistency, but it will decrease with the complexity of PIP process increasing. The mechanical properties of 2D composites can be well characterized by multifilament composites, and the process parameters of 2D composites fabricated by PIP process can be optimized primarily, which can enhance the process design efficiency obviously.