All the species of Macrostomum are hermaphrodite and have only one set of male copulatory organs. In this study, the authors found two specimens of Macrostomum (deformed Macrostomum sp. 1 and deformed Macrostomum sp. 2) which have duplicated male copulatory organs in the freshwater environment for the first time in Guangdong Province in 2015. With the observation of living bodies, dyed specimen and whole body sections (Fig. 1, Fig. 2), we found that their two sets of copulatory organs arrange in a left- to right-hand sequence. Each set of copulatory organs has an intact false vesicula seminalis, vesicula seminalis, vesicula granulorum and penis stylet. The false vesicula seminalis and vesicula seminalis contain numerous spermatozoa. And they have one and two male gonopores, respectively. In addition, these four penis stylets′ structures are different from those of the species of Macrostomum that have been recorded in China. In this paper, morphology of these two specimens are described in details (Table 1) and the reasons why these phenomena happened are briefly discussed.