Abstract: The genus Mallomonas belongs to Synurales, Synurophyceae, Chrysophyta, it was created by Perty in 1852 and reported as one of the largest genera in Chrysophyta. Algae of the genus including solotary colored monads with the cells covered with silica scales were regularly arranged as imbricate or armor shape, or freely. Some scales bear bristles and some do not. They were considered as the most important taxonomic characters for species determination and species taxonomy. Because of their narrow ecological optimum, the species of  Mallomonas were considered as the valuable bioindicators of both recent and historical environments, especially in paleolimnology. Based on the study of specimens and literatures, 9 species of  Mallomonas  in Shanxi Province are reported in this paper for the first time, and they are M. caudata, M. oviformis, M. insignis, M. striata, M. areolata, M. elongata, M. tonsurata, M. costata and M. acaroides. These new records make the materials about algae in Shanxi Province be abundant.

Key words: Chrysophyta, Mallomonas, plant specimen, new record, Shanxi Province