Abstract: Detaited studies on the microstructure,coal-forming plants and sporopollen assemblage of light brown coal from Tertiary in Yunan province are made in this paper by the methods of coal petrology, phyteral analysis and TEM & SEM technology. We also make a study of light brown coal compared with the dark brown coals and peats derived from different plants. On the basis of the above studies, we put forward a new theory on the coal-forming plants and genesis of the light brown coal in Yunnan Province.