Abstract: In order to improve the mechanical properties of phenolic foam(PF), phenolic foam composites reinforced by hollow glass beads (HGB) were prepared by compression molding. The compressive property and thermal stability of the composites were evaluated by mechanics performance test, TG analysis and vertical burning method, and the strengthen mechanism were also analyzed. The results show that when the mass ratio of HGB to PF reaches 10%, both of the compressive strength and compressive modulus of PF/HGB reach the maximum value. Pretreated with silicane coupling agent, the compressive strength and compressive modulus of hollow glass beads reinforced phenolic foams improve substantially. TG analysis and vertical burning method show that HGB as filler reduces thermal degradation rate of foam, leading to slightly higher thermal stability but slightly lower flame resistance. Analyses by SEM, FTIR and EDS reveal that the breakage behavior of PF/HGB is breakage of the cells, which leads to the HGB debond or rigid fracture. The froth density of PF/HGB increases, frothy diameter decreases, the interfacial adhesion between the surface of hollow glass bead and PF matrix is good, and hollow glass beads disperse homogeneously in PF matrix.