Most dielectric spectroscopy techniques require careful system calibration, tedious measurement, specially designed probes, precise input source and some even involved complicated inversion models. This study presented two robust and model-free signal processing approach to extract frequency-dependent dielectric properties from time domain reflectometry (TDR), namely phase velocity analysis (PVA) and multiple reflection analysis (MRA). PVA determines frequency-dependent apparent dielectric permittivity (ADP) from the top and end reflections in TDR signal. MRA encompasses all multiple reflections of TDR signal to measure the complex dielectric permittivity (CDP) spectrum. This innovative approach involves decomposing the first top reflection and the subsequent multiple reflections from TDR signal, comparing their spectral MRA-ratio and inverting the frequency-dependent CDP from the measured MRA-ratio. Both their reliability were evaluated numerically and experimentally from 10MHz-IGHz. Since they are independent of source function and preceding system mismatches, dielectric spectroscopy can be conveniently conducted in laboratory and field, without complicated system setup and calibration.