Myxomycetes (true slime molds) are amoebozoan protists involved in decomposition and nutrient cycling in terrestrial ecosystems. Recent molecular studies have led to major taxonomic revisions in Physaraceae, including the establishment of the genus Nannengaella for highly calcified species previously placed in Physarum. To refine the taxonomy and distribution of Nannengaella in China, we used an integrative approach combining multilocus phylogenetics and morphological examination. A total of 149 specimens from 14 provinces and autonomous regions in China were studied, and phylogenetic analyses were conducted using five loci: nSSU, EF-1α, mtSSU, α-tubulin, and COI. Results confirmed that Nannengaella is a distinct and monophyletic lineage within Physaraceae. One new species, Nannengaella luteotestacea, is described as a well-supported lineage in the genus, and three former Physarum species (N. herbatica, N. cremilutea, N. conglomerata) are recombined into Nannengaella based on molecular and morphological evidence. New distribution records in China are provided for several species: N. herbatica from Jilin Province, N. cremilutea from Heilongjiang, Shaanxi, and Henan Provinces, and N. conglomerata, N. contexta, N. sulphurea, and N. leucopus from Sichuan Province. Detailed morphological descriptions, voucher information, ecological notes, and an identification key are also presented. These findings improve the taxonomic framework of Nannengaella and enhance understanding of its diversity and biogeographic distribution in China.