Abstract: Three micron spindle-shaped PbWO₄ with different microstructures are synthesized by varying the concentration of the surfactant CTAB (cetyltrimethylammonium bromide) and the reaction time. The synthesized and commercial PbWO₄ are used as fillers, and mixed with B₄C and HDPE (high-density polyethene) to prepare composites for neutron and gamma-ray radiation shielding. X-ray diffraction (XRD) analysis reveals that the growth priority of the four main crystal planes of PbWO₄ is: (200) > (312) > (112) > (204). Field emission scanning electron microscope (FESEM) and specific surface area analyses reveal that PbWO₄ undergoes Ostwald ripening and oriented attachment mechanisms to form morphologically regular micron spindle-shaped microstructures, and their specific surface areas (S_BET) are 0.64 m²/g, 1.02 m²/g, and 1.76 m²/g, respectively. The commercial PbWO₄ is an irregular structure and large-sized bulk with a much lower S_BET of 0.21 m²/g. The thermostability and mechanical properties such as melt temperature (T_p) and yield stress (σ_y) of micron spindle-shaped PbWO₄-B₄C/HDPE composites are better than those of commercial PbWO₄-B₄C/HDPE. Pb has good ductility and can improve the tensile stress and toughness of the material. The neutron and gamma-ray radiation shielding tests show that the micron spindle-shaped PbWO₄-based composites with high specific surface areas have much better shielding performances than the commercial PbWO₄. The composite with the best radiation performance has a total neutron cross-section (Σ) of 0.22 cm⁻¹ for ²⁵²Cf neutron source and a linear attenuation coefficient (μ) of 0.099 cm⁻¹ for ¹³⁷Cs gamma-ray source.