In recent years, the research of liquid crystal microwave communication devices has developed rapidly. The high dielectric loss of liquid crystal materials has become a bottleneck restricting the development of microwave devices. There are few reports on the properties of liquid crystal materials at microwaves. Therefore, we take the fluorine substituted tolane-type compounds with low melting point and high birefringence as the research object, doping them into the liquid crystal matrix MA in a certain proportion respectively, and testing them at microwave k-band (10~30 GHz) through the rectangular cavity perturbation method. And then, the influence of molecular structure on the dielectric properties of liquid crystals at microwave frequency is discussed.The experimental results show that dielectric anisotropy at high-frequency is related to the polarity of liquid crystal molecules and birefringence. The lateral fluorophenyl phenylacetylene and terminal isothiocyano phenylacetylene liquid crystal compounds exhibit high dielectric anisotropy(Δεr>0.85). Triphenyl diacetylenes substituted by F-atom symmetrically and triphenyl acetylene liquid crystal compounds with terminal isothiocyanate exhibit lower dielectric loss(tanδεr⊥<0.008,18 GHz) due to higher birefringence. Fluorinated diphenylacetylenes with terminal isothiocyanates and triphenyldiyne substituted with fluorine asymmetrically liquid crystal compounds show higher dielectric loss(tanδεr⊥>0.008, 18 GHz).