Abstract: The electromagnetic pollution caused by electronic equipment to the external environment has become another major public hazard after noise pollution, air pollution, water pollution and solid waste pollution, so the research and development of high-performance electromagnetic shielding materials has become a hot spot in materials science research. In this paper, the phase domain size of the polymer phases in the PP/PBT/CNTs blends was regulated by adjusting the blending methods of polypropylene (PP), polybutylene terephthalate (PBT) and carbon nanotubes (CNTs) during the melt blending process. The influence of the microscopic morphology of the composites on their electromagnetic shielding properties was studied by morphology analysis, dynamic rheology and crystallization behavior tests. The results show that compared with the PP phase, CNTs have a stronger affinity for the PBT phase, and are always located in the PBT phase domain among the four blending methods. When the PP/PBT/CNTs composites are prepared by PP/CNTs masterbatch method, the phase domain size of the PBT inside the obtained composites is smaller, the compatibility between PP and PBT is higher, the conductive path and interface area are significantly increased, and a denser and uniform conductive network structure is formed inside the composites, so the conductivity of the prepared polymer matrix composites is significantly improved, reaching 29.60 S/m, and the electromagnetic shielding efficiency is in the X-band (8.2-12.4 GHz) to 35.6 dB, far exceeding the demand for commercial electromagnetic shielding materials.