The microphysical characteristics of multi-layer stratiform clouds in autumn are examined using layered vertical observation data of Particle Measuring Systems (PMS) obtained during an airborne observation experiment over the Sanjiangyuan National Nature Reserve. Results show that cirrostratus (Cs) and upper-level altostratus (As) are ice-phase clouds, while lower-level As and stratocumulus (Sc) are supercooled mixed-phase clouds. The particle concentration and the content of supercooled water of the lower level As are the largest in the cloud system. The Sc particle size and spectral width are the largest and shows clear regional characteristics. The median diameters of the Sc (lower As and convective bubble) cloud particles are 3.5-18.5 μm (3.5-21.5 μm) for the liquid phase and greater than 21.5 μm (24.5 μm) for the ice phase. The differences between the higher and lower supercooled water in the cloud particle spectra are distinguished. The high supercooled water area of Sc exhibits an obvious rime growth phenomenon. The effective radius of droplets becomes increasing large in Sc, at the bottom of the lower-level As, and on the top of the convective bubble. The content of supercooled water of the high subcooled water area has a mean ratio and standard deviation of 69.9±19.4%. In addition, the fraction of liquid water in Sc is related to the supercooled liquid water content in the high content of water, but there is no obvious variation in the lower-level As, which shows a mean ratio and standard deviation of 89.2±8.1%. The cloud particle spectrum in the mixed-phase cloud observed by the Forward Scattering Spectrometer Probe (FSSP) and the Two-Dimensional Cloud Probe (2DC) are respectively in single-peak Γ and negative exponential distribution.