MoO3 is a well-known multifunctional material which can be potentially used in a distinct gas-sensing applications. In this study, we grow the large-scale nanonetwork composed of α-MoO3 nanosheets by using conventional chemical vapor deposition method. The microscopic and spectroscopic characterizations confirm the continuity and crystallinity of the deposited MoO3 film. The dynamic response resistance of the device reveals a high sensitivity of 53% for 1% hydrogen at 180 °C. A detailed gas-sensing mechanism was explained by the depletion-layer modulation process. © 2019 IEEE.