We report an optimized monolithic dual-wavelength distributed feedback (DFB) laser for terahertz (THz) applications, designed to address the challenges of complexity, cost, and power efficiency in a THz transmitter. This laser can achieve a high optical power of 65.93 mW. Under a wide temperature range and high-bias current, the power difference between the two primary modes remains below 1 dB, with each side-mode suppression ratio exceeding 36 dB. Additionally, the two primary modes exhibit low relative intensity noise peaks of -153.88 dB/Hz and -153.46 dB/Hz and narrow linewidths of 117.33 kHz and 70.59 kHz, demonstrating stable and high-performance dual-wavelength operation. These results underscore the potential of the dual-wavelength (DW)-DFB laser as a compact and cost-effective solution for THz systems.