Abstract: Near-infrared reflectance spectroscopy enables the identification of water bodies, vegetation, and various altered minerals within the near-infrared spectral region. The utilization of near-infrared spectroscopic instruments for mineral mapping represents an advanced technology widely-adopted in contemporary geological work, demonstrating substantial significance for technological innovation and enhancement of green exploration equipment. This article presents research on a spectrometer operating in the 950–1650 nm spectral range utilizing an InGaAs detector developed to address the requirements for field-based online analysis. The study examines the dark current composition in InGaAs detectors and its temperature dependence. The spectrometer’s optical system implements a concave grating spectrometry method, eliminating the need for focusing lens and simplifying the optical path; The electronic system incorporates a CY7C68013A single-chip computer core with USB 2.0 communication. The instrument achieves a spectral resolution better than 6nm, a reflectivity deviation less than 0.4%, linearity better than 0.02, and measurement speed of 20 measurements per second, while maintaining a weight of 3.5 kg (including battery). Spectral tests conducted on green leaves and soil samples under direct sunlight, compared with third-party test data, demonstrate effective spectral signal acquisition. The instrument exhibits superior characteristics in detection rate, measurement speed and miniaturization.