In the present study, we selected 54 natural Miscanthus lutarioriparius populations to study their geographical distribution pattern and phenotypic diversity. These selected populations evenly distributed in the naturally occurrence range of M. lutarioriparius across China. Their phenotypic traits were measured during the field investigation conducted at the end of 2017 growing seasons, including the plant height, stem diameter, pitch number, length of the longest stem, branch number, shoot density, dry weight per stem and dry matter yield. And the soil pH and soil fertility were also determined. The effects of soil factors on these phenotypic traits and correlations between these phenotypic traits were further studied. Results showed that: (1) eight phenotypic traits were significantly (P＜0.01) different between and within the 54 natural M. lutarioriparius populations, and the phenotypic variation mainly came from within the population. (2) There were significant correlations within these eight phenotypic traits. For example, the plant height positively correlated (P＜0.01) with the pitch number and stem diameter, while significantly negative correlations existed between the shoot density and the other phenotypic traits. Length of the longest stem only had significant correlations with the plant height. (3) Information of the eight phenotypic traits were summarized to four principal component factors, namely the yield factor, plant type factor, shoot density factor and longest stem factor. These four principal component factors could reflect 84.436% phenotypic information of the 54 natural populations. (4) The 54 natural M. lutarioriparius populations were clustered into two groups based on the cluster analysis of their phenotypic traits. The first group contained 23 populations naturally distributing at the lower reaches and the northeast of the Yangtze River. The second group contained 31 populations mainly from the Dongting Lake area, the middle reaches and the northwest of the Yangtze River. Plants in the second group generally had higher plant height and biomass yield, smaller shoot density, thicker stem than that from the first group. (5) The natural M. lutarioriparius populations mostly grow on the infertile soil with a nearly neutral pH. The soil organic matter content and available potassium content had the greatest influence on the plant height of M. lutarioriparius, which was suggested by their high direct path coefficients of 0.443 and 0.318, respectively. That was also true for their effect on the biomass yield with their direct path coefficients of 0.259 and 0.429, respectively.