Abstraction: Change of ultrastructure of Chlorella vulgaris caused by magnetic treatment was investigated by transmission electron microscopy. Chloroplasts, mitochondria and vacuoles were sensitive to magneticreatment. The observation result showed that plasmolysis appeared together with the increasing of the number of vacuoles, mitochondria and starch granule when the magnetic intensity rose. The vacuoles and pigment bodies swelled up and the structure of thylakoid was injured slightly. The result showed that the growth and metabolism of Chlorella vulgaris was influenced in different extent because of changes of two cell energy supply systems in pigment bodies and mitochondria caused by magnetic treatment.