Developing efficient drug-detecting technologies is critical to the fight against their related abuse and trafficking crimes. In the present work, a novel morphine detection device based on metal-oxide-semiconductor (MOS) gas sensors with low-cost, highly sensitive, and portable is designed and fabricated. The exclusive sensitive material, ZnO nanoparticles self-assembly porous networks (ZnO-N) with ample oxygen vacancies (OV) defects prepared by PVP-chelated precipitation followed by a chemical blowing calcination method, is decisive to morphine drug identification. OV defects can modulate the intrinsic electronic structure and endow ZnO-N with more suitable band structures for enhancing oxygen species adsorption and morphine molecules oxidation. The optimal ZnO-N-2 sensor exhibits positive linear relationship response values of 1.1–8.8 in the concentrations of 2–200 ppm toward the standard morphine drug sample at the optimal operating temperature of 250°C. More importantly, the homemade portable device equipped with the ZnO-N-2 sensor can accurately identify the morphine drug and perform early warning. This work innovatively demonstrates the feasibility of MOS gas sensors for the detection of stashing morphine drugs in methanol, which is of great significance for effectively combating global drug-related crimes.