To provide direction and guidance for the microstructure design and development of sealing materials for high-performance intermediate-temperature solid oxide fuel cell, a Al2O3/BaO-CaO-B2O3-Al2O3-SiO2 glass-ceramic (BCBAS)-based composite sealing material with superior mechanical properties and a high thermal conductivity was prepared via tape casting. According to the analysis by scanning electron microscopy and X-ray diffraction, the lamellar Al2O3 is regularly distributed in the BCBAS glass-ceramic matrix. The main crystallization phase of BCBAS glass transforms from Ca0.1Ba0.9SiO3 into Ba1.55Ca0.45SiO4 and BaAl2Si2O8, and further into BaAl2Si2O8 and BaAl2O4 phases when the lamellar Al2O3 content increases from 0 to 25% (in mass fraction). The thermal conductivity of biomimetic sealants increases from 0.892 W/(m·K) to 1.255 W/(m·K), and the bending strength and Vickers hardness with higher than 10 of the Weibull modulus β increase from 96 MPa to 140 MPa and 444 HV to 677 HV as the lamellar Al2O3 content increases from 0 to 25% (in mass fraction), indicating the mechanical properties and thermal conductivity of the sealant. The sealing tensile strength of the biomimetic sealant with the mass fraction of lamellar Al2O3≤20% maintains above 4 MPa. The composite with 20% Al2O3-80% BCBAS glass exhibits the superior comprehensive properties (i.e., thermal conductivity of 1.203 W/(m·K), bending toughness of 136 MPa, Vickers hardness of 677 and sealing strength at 4.22 MPa), thus being a potential candidate for application of intermediate- temperature solid oxide fuel cell.