  Low sky brightness is crucial for ground-based astronomical observations,
because it limits the observational capability to detect fainter sources.
Lenghu, located on the Tibetan Plateau in China, has been identified as an
high-quality astronomical site in China, including dark sky in optical band. In
this work, we will report the preliminary results of near-infrared sky
brightness measurements at Lenghu. Utilizing a wide-field small telescope
equipped with an InGaAs camera, we have been conducting long-term monitoring of
near-infrared sky brightness in the J and H' bands, respectively, since January
2024. For each image, photometry and astrometry were performed, then sky
background was calibrated by standard stars from the 2MASS catalog. This report
includes preliminary results on the sky brightness at zenith in the J and H'
bands, as well as their variations with solar elevation at Lenghu. Our initial
results indicate that the near-infrared sky brightness at Lenghu is comparable
to that of other world-class sites, and long-term monitoring will be continued.
