Abstract: The adoption of composite materials in substation insulators is expected to improve the seismic performance of electrical equipment. The dynamic properties, bending stiffness, and strength of a composite insulator are tested, and the results are employed in FE modeling of electrical equipment which uses the composite insulator. The seismic fragility of the equipment is analyzed based on the theory of Probabilistic Seismic Fragility Analysis (PSFA). The results show that adhesive joints between composite tube and metal flange are a weak point in bending, and the stiffness of the adhesive joint is smaller than that of composite tube. When subjected to a 0.4 g level ground motion, seismic fragility of the equipment formed by composite insulators is small for moderate and severe levels of damage, but as large as 38% for minor level of damage. Increasing the flexural strength of adhesive joint can be effective in improving seismic performance. Taking the failure probability as index of seismic fragility, the paper presents a probabilistic evaluation of eletrical equipment's seismic performance.