By measuring the electrical resistivity of RTV silicone rubber with Ni powder, t he percolation threshold of Ni-based conductive silicone rubber was determined. When N234 was filled in Ni-based conductive silicone rubber,double-percolation p henomenon was found other than percolation law. After fitting of the experimenta l results,the mechanism of the double-percolation phenomenon was presumed. As fo r the shielding effectiveness of high conductive silicone rubber, the result sh ows that it can be described well with the Schelkunoff theory.The influence of double-percolation phenomenon on shielding effectiveness of the rubber was investigated.