Abstract: The increasing demand for dispersion engineering in various photonic applications necessitates spectrometry with both kilohertz resolution and several terahertz bandwidth. A laser with sufficiently large frequency tuning range is required in traditional methods, Yielding bulky and expensive systems that are difficult to integrated on a chip. Compact, high-resolution, and broadband spectrometers are crucial, yet on-chip integration, particularly of the optical source, remains challenging. Here, we propose a 5.2-THz-bandwidth miniaturized spectrometer utilizing a laser only in GHz tuning range. The laser’s tuning range is leveraged by integrated Si₃N₄ soliton microcombs to achieve a 650-times larger measurement bandwidth, extending the measurement range from 1525.3 to 1566.8 nm and surpassing the optical C-band. The soliton microcomb is meticulously frequency-stabilized, achieving frequency fluctuations below 100 Hz, ensuring high frequency precision for our spectrometer. By combining optical asymmetrical double sideband modulation with soliton microcombs, we significantly enhance the spectrometer’s performance, offering higher resolution, larger dynamic range, and greater bandwidth. This optical spectrum measurement approach enabled by GHz-tunable laser opens a way to significantly simplify system complexity.