Cloud droplet spectral relative dispersion is critical to the aerosol-cloud-radiation interaction and the formation of surface precipitation. This study discusses the relationship between relative dispersion of cloud droplet size distributions and volume-mean radius by analyzing the observation data from April to July 2008, May to August 2009 and May to September 2011 at the Guangming Peak of Huangshan. This relationship is often used to parameterize relative dispersion. The results show that the relationship between relative dispersion and volume-mean radius changes from positive to negative with the increase of the volume-mean radius, which is mainly related to activation, condensation, evaporation and deactivation, consistent with previous studies. It is further found that the negative correlation is relatively weak, mainly due to collision-coalescence. When the autoconversion threshold function increases, the correlation between relative dispersion and volume-mean radius turns from negative to positive, and the degree of positive correlation gradually increases due to enhanced collision-coalescence. The positive correlation caused by collision-coalescence offsets the negative correlation caused by condensation and evaporation. In addition, although some cloud droplet size distributions have double peaks, the first bin strength (the first bin number concentration divided by the total number concentration) can still well distinguish their positive and negative correlations. These results will enhance the theoretical understanding of the influencing factors of relative dispersion, which is conducive to the improvement of relative dispersion parameterizations.