The invention relates to a glass fiber with a low dielectric constant for a high frequency high-density circuit board, which is characterized in that: the glass fiber comprises the following components in percentage by weight: 50 to 60 percent of SiO2, 12 to 18 percent of Al2O3, 0 to 1.8 percent of CaO, 0.5 to 3.2 percent of MgO, 0.5 to 3.2 percent of ZnO, 21 to 27 percent of B2O3, 0 to 0.25 percent of Li2O, 0 to 0.25 percent of Na2O, 0.4 to 4 percent of TiO2, 0.5 to 3 percent of CaF2, and 0.2 to 0.6 percent of CeO2. The glass fiber disclosed by the invention has the advantages of excellent water resistance, excellent adhesion with the resin and easy follow-up processing. At room temperature, when the frequency is 1MHz, the dielectric constant is between 4.2 and 4.6 and the dielectric loss factor is between 10*10<-4> and 12*10<-4>. The glass fiber is particularly suitable to be used as a reinforcing material of the high frequency high-density multilayer interconnection printed circuit board.