Abstract: Multilayer circuit substrate technology provides an excellent solution for miniaturized design of electronic systems, and has become one hot spot of the research. In multilayer circuit substrates, the performance of via-holes, as the core circuit unit for connecting the transmission lines and components laying on the different layers, directly affects the characteristics of the whole electronic system. In this paper, a microstrip line-strip line-microstrip line (MS-SL-MS) via-holes transition in W-band is designed and fabricated based on the multilayer liquid crystal polymer (LCP) substrate technology. In order to suppress the parasitic effect between the via-hole and the substrate, the defected ground structure (DGS) has been introduced, which significantly improves the millimeter-wave performance of the via-holes transition. Simulation results show that the return loss of the via-holes transition is less than -20.9 dB and the insertion loss is better than 1.58 dB in W-band, and in order to verify the validity of the simulation, multilayer LCP substrate have been fabricated, and the measured results show that, in W-band, the return loss of the circuit is less than -10 dB and the insertion loss is better than 3 dB, which can satisfy the broadband transmission of millimeter-wave signals, this low-loss via-holes transition can be applied to millimeter-wave circuit packages.