Glazed hollow beads, cement, fly ash, polypropylene（PP） fibers and carbon nanotubes were used to prepare composite thermal insulation materials.The surface microstructure of unmodified and modified PP fibers, the fracture profile of samples and the active functional group of PP fibers were analyzed by SEM and IR to study the effects of modified PP fibers on mechanical property of the composite thermal insulation materials. The SEM was adopted to analyze the fracture profile of composite thermal insulation materials, to study the effects of carbon nanotubes on strength and electromagnetic shielding effectiveness of the composite thermal insulation materials. The results show that active functional group —OH and—COOH are introduced into modified PP fibers. Compared to the samples mixed with unmodified PP fibers, the flexural and compressive strength of samples mixed with modified PP fibers increase by 2069% and 1176%, respectively. After adding carbon nanotubes, the flexural and compressive strength of composite thermal insulation materials are improved significantly, the electromagnetic shielding effectiveness of materials is also improved significantly when electromagnetic radiation frequencies are between 515 GHz.