Abstract: After firing in different season, some characters of Songnen grassland varied obviously. As compared with unfired or fired in Spring, the soil water content was lowered after fired in Autumn, but little difference was found after fired at different periods of Spring. The grass yield, population composition and species diversity after fired in Autumn were significantly lower than those after unfired or fired in Spring, but the species of annual plant increased. No significance difference was found in grass yield after fired at different periods of Spring, but top bud species decreased after fired in late Spring. Different life form species had different response on the same firing, not only in their individual growth, but also in their yields.

Key words: Burning, Production, Composition, Diversity, Grassland