In this study, inspired by the frequency-modulated continuous-wave (FMCW) method, an operation scheme of continuous-wave (CW) terahertz (THz) homodyne system is proposed and evaluated. For this purpose, we utilized the fast and stable wavelength tuning characteristics of a dual-mode laser (DML) as a beating source. Using the frequency-modulated THz waves generated by DML, a cost-effective and robust operation of CW THz system to be applicable to the measurements of thickness or refractive index of a sample is demonstrated. We believe that the proposed scheme shows a potential to the implementations of compact and fast CW THz measurement systems that can be useful in many THz applications.