Abstract: The studies on Miscanthus spp, Phragmites australis, Pennisetum are very rare. But they distribute in a large area on the middle and lower reaches of the Yangtze River in China. These grasses have not fully utilized. In order to develop biomass utilization and provide another way for a better future, in order to provide experimental data for a more rational and efficient use of these grasses, this article mainly made the thermogravimetric annlysis of Miscanthus spp, Phragmites australis, Pennisetum, comparing rice straw. The pyrolysis characteristics were obtained using TG and DTG curves. A pyrolysis index, D, was used to describe the biomass pyrolysis characteristics. And kinetic parameters of biomass were also calculated by thermal analysis mathematic method. The results show that the pyrolysis process of these samples could be separated into four stages. Biomass have a shoulder volatilization peaks at about 563 K. The main weight loss occurs from 460 K to 673 K. The pyrolysis index D is Miscanthus spp > rice straw > Pennisetum > Phragmites australis. The activation energy is Miscanthus spp > rice straw > Pennisetum > Phragmites australis. The char yield is Miscanthus spp > Pennisetum > rice straw > Phragmites australis. Generally speaking, thermal stability of Miscanthus spp is relatively poor, Phragmites australis is relatively stable. The pyrolysis process can be described by second order reaction model,with the method of Coasts-Redfern, the activation energy and frequency factor of different kinds of floristic biomass were attained.