Variations in cloud microphysical characteristics significantly impact weather and climate, making them a key focus in cloud precipitation physics research. Cloud droplet spectral dispersion is a crucial parameter for characterizing cloud microphysical processes and plays a fundamental role in studies of aerosol-cloud-precipitation interactions. Although extensive research has been conducted on cloud droplet spectral dispersion and its influencing factors, significant uncertainties remain due to variations in study regions, observation methods, and cloud developmental stages. These uncertainties pose challenges in addressing aerosol indirect effects. The northeastern Qinghai-Xizang Plateau is a climatically sensitive region where the plateau monsoon and the East Asian monsoon converge, making it highly susceptible to global climate change. A series of aircraft observation experiments have been conducted in this region, primarily focusing on cloud structural characteristics. However, limited attention has been given to cloud droplet spectral dispersion. Based on in situ aircraft observations of microphysical properties in typical supercooled stratiform clouds over the northeastern Qinghai-Xizang Plateau on April 27, 2022, this study analyzes the vertical distributions of cloud microphysical properties and cloud droplet spectral characteristics. The key findings are as follows: 1) The spectral width of cloud droplets was larger in the lower layers due to entrainment and weak activation processes. In the middle of the cloud, the activation of numerous aerosols led to competitive water vapor consumption among cloud droplets, limiting droplet growth and reducing spectral width. In the upper cloud layers, droplet condensation growth further decreased spectral width. 2) When the liquid water content and cloud droplet number concentration were below threshold values of 0.025 g·m^－3 and 30 cm^－3, respectively, cloud droplet spectral dispersion exhibited a wide range (0.30—0.85). However, above these thresholds, spectral dispersion decreased and remained within a narrower range (0.3—0.5). 3) Compared to the standard deviation of the cloud droplet spectrum, variations in aerosol concentration primarily influenced the mean cloud droplet radius, which dominated the negative correlation between aerosol concentration and cloud droplet spectral dispersion. 4) Cloud droplet spectral dispersion is a critical factor that must be considered in the parameterization of the cloud-to-rain autoconversion process. A positive correlation was observed between the automatic conversion rate and cloud droplet spectral dispersion, indicating that larger spectral dispersion facilitates the conversion of cloud water into rainwater. To further understand the mechanisms driving variations in cloud droplet spectral width, future research should focus on targeted aircraft observation experiments that simultaneously measure aerosol properties and cloud microphysical parameters.