Abstract: Myxobolus haichengensis Chen, 1958 forms numerous small plasmodia on the gill filaments of wild cyprinid Abbottina rivularis Basilewaky. The species described originally was lacking important characters, which made the accurate identification difficult. Here, we supplemented its characteristics with morphological and molecular data. Plasmodia of M. haichengensis are oval. Mature spores are ellipsoidal-shaped in frontal view and fusiform-shaped in lateral view, measuring (10.8±0.7) μm (10.1—11.5 μm) long, (8.1±0.5) μm (7.5—9.0 μm) wide, and (5.7±0.4) μm (5.2—9.0 μm) thick; two unequal polar capsule are pyriform with tapering anterior, large polar capsule averaging (4.7±0.5) μm (4.8—6.7 μm) long and (2.5±0.2) μm (3.2—4.3 μm) wide; small polar capsule averaging (4.4±0.2) μm (4.1—4.8 μm) long and (2.2±0.1) μm (2.0—2.5 μm) wide; polar filaments coil with four to five turns. The nuclear 18S rDNA sequence was obtained and deposited in GenBank (KY965936), and sequences alignment analyses revealed that M. haichengensis was most similar with the actinosporean Hexactinomyxon type 2 (AY162272, 97%) released from the freshwater tublificid oligochaete Limnodrilus hoffmeisteri.