Atomically thin layers of transition-metal dicalcogenides (TMDCs) are often known to be metastable in the ambient atmosphere. Understanding the mechanism of degradation is essential for their future applications in nanoelectronics, and thus has attracted intensive interest recently. Here, we demonstrate a systematic study of atomically thin WTe 2 in its low temperature quantum electronic transport properties. Strikingly, while the temperature dependence of few layered WTe 2 showed clear metallic tendency in the fresh state, degraded devices first exhibited a re-entrant insulating behavior, and finally entered a fully insulating state. Correspondingly, a crossover from parabolic to linear magnetoresistance, and finally to weak anti-localization was seen. Real-time Raman scattering measurement, together with transmission electron microscopy studies done before and after air degradation of atomically thin WTe 2 further confirmed that the material gradually form amorphous islands. It thus leads to localized electronic states and explains the low temperature Coulomb gap observed in transport measurements. Our study reveals for the first time the correlation between the unusual magnetotransport and disorder in few-layered WTe 2 , which is indispensable in providing guidance on its future devices application. [4,5]. Albeit a layered material, WTe 2 devices in the two-dimensional (2D) limit have been rarely reported, with its experimental investigations mostly restrained in the bulk regime. Unlike other transition-metal dichalcogenides (TMDCs), instead of 2H phase, Td-(also addressed as 1T'-) phase of bulk WTe 2 occupies the lower energy state, whose two nearly perfectly compensated electron and hole bands result in a large unsaturated classical magnetotransport, with a parabolic dependence of the applied magnetic field B [6]. Meanwhile, strong anisotropy was found in its bulk form, which gives rise to some exotic linear magnetoresistance in a specific measurement configuration [7]. Moreover, recent angle resolved photon electron spectroscopy (ARPES) studies showed subtleness of the band structure of bulk WTe 2 [8][9][10][11], intriguing possible peculiar electronic properties in the few layered scenario. In the 2D limit, electrostatic gate can, in principle, largely tune the carrier density, thus breaking down the electron-hole balance, leading to new opportunities.Despite the fact that WTe 2 can be readily exfoliated against the weak interlayer van-der-Waals bonding, atomically thin WTe 2 is proven to rapidly age in ambient atmosphere like many of the TMDCs [12]. Together with the extinction of optical contrast and Raman signal after air exposure [13], ultra thin WTe 2 flakes were reported to exhibit, rather than the so-called semi-metal state, an insulating behavior as a function of number of layers, with the lack of a systematic analysis of the aging effect on the quantum transport [14]. Such air instability therefore hampers the further possibilities for nanoelectronic devices of, for example, few-layered WTe 2 fi...