Due to the transparency to the terahertz waves, many polymeric materials have been demonstrated various important applications as optical components as well as dilution matrix for terahertz research. Certain dielectric responses are usually preferred considering different application circumstances. The adjustment of dielectric property could be achieved by proper selection of polymer as well as design of polymer blend by physically mixing. Methodology is well described in this study for the terahertz dielectric analysis of polymeric materials and their mixtures in a quantitative manner, as exemplified by experiments with polyethylene (PE) and polytetrafluoroethylene (PTFE) for their widespread applications in terahertz research. Following the regular procedure of measuring the THz dielectric property of single component pellets with the phase delay information provided by the coherent detection of terahertz time domain spectroscopy, the intrinsic dielectric constants of PE and PTFE were determined as 2.315±0.003 (±0.13%) and 2.109±0.003 (±0.14%) by removing the influence of trapped air utilizing effective medium theory (EMT). These measured values were then used to simulate the THz dielectric constants of mixture pellets consisting of PE and PTFE at several mass ratios combing with EMT. The comparison between simulated values and experimental values of mixture samples presents a well linear correlation with R2=0.964 3 while the overall relative difference is 1.08%.