Abstract: An immobile freshwater dinophyceaous alga Cystodinium balaviense Klebs belonging to Phytodinales was found in a little humus pool from Hubei province,China.This order is new to China.The morphology and life history are described from the fleld and laboratory materials.The vegetative cell of C.bataviense is near lunate, the division of one cell results in tWo zoospores.Aplanospore or cyst will form when environment is rough.Aplanospore is globular, it's found from a vegetative cell by itS shrinkage.Cyst is derived from the protoplast of a mother cell,its outer wall ornament with many appendages like some "annular mountains".The cyst of C.bataviense is first reported for this genus.