We synthesize composite systems of multi-wall carbon nanotubes (MWCNTs)/SiO2 by using the sol-gel method.The dielectric properties of the systems with different-concentration MWCNTs are studied.In our MWCNTs/SiO2 inorganic systems,the twin-percolation phenomenon exists when the concentrations of MWCNTs are 5-10％ and 15-20％.The permittivity and conductivity have jumping changes.The twin-percolation phenomenon is attributed to the special transfer mechanism of MWCNTs in the system,determined by hopping and migrating electrons.Variations of dielectric properties and conductance of the M WCNTs/SiO2 systems are conformed to the percolation theory.The special percolation phenomenon and electric properties of MWCNTs/SiO2 can help us comprehend the conductivity mechanism of the MWCNTs/SiO2 systems effectively,and promote the development of a high performance function composite system.In recent years,one-dimensional (1D) nanomaterials,and especially 1D carbon nanomaterials,have attracted extensive interests due to their unique properties in various fields,such as physics,[1-4] chemistry,[5-8] and materials.[9,10] Carbon nanotubes (CNTs)[11-14] with unique one-dimensional nanostructures are widely used in field emission devices,hydrogen storage and microwave absorption,making them a good candidate for practical applications.