In response to the growing demand for moisture detection across various industries in our country, near-infrared spectroscopy offers the advantage of non-contact measurement. However, existing equipment often suffers from drawbacks such as large volume, high power consumption, and difficulty in modulating optical signals. Furthermore, the core technology is still monopolized by foreign manufacturers. In this study, a detection scheme using a light-emitting diode (LED) with a 1450 nm detection band and 1200 nm reference band is proposed for the measurement of the light source. A portable near-infrared moisture detector was developed using nondispersive infrared technology, and relevant gradient moisture detection experiments were conducted on crops. The experimental results showed that the instrument was stable and performed well in the moisture content test of wheat kernels; furthermore, its moisture content discrimination was high. In addition, the instrument had a fast response speed and convenient light source frequency modulation. After further optimization, this instrument can be widely used for nondestructive real-time online moisture detection.