Abstract: Dry climate, overgrazing, damaged by rats and invasion of poisonous grass species are the main causes resulting in a degeneration of grasslands, and poisonous grasses have already resulted in a direct menace to all kinds of grasslands. In order to provide a rational scientific base, the distribution of poisonous grass species in natural grasslands in Urumqi County was studied. According to the identification of plant specimens, there were 46 main poisonous grass species in 29 genera and 17 families in the county, and their proportion was 5% of the total. The distribution area of poisonous plant species was 3.27×10⁴ hm², and it occupied 9.83% of the total grassland area. The main poisonous grass species included Achnatherum inebrians, Peganum harmala, Anabasis aphylla, Stipa capillata, Sophora alopecuroides, Thermopsis lanceolata and Pedicularis oederi. These poisonous plants were perennial herbs, their reproductive capacity was very strong, their growth was rapid, and these poisonous plants were high and competed sunshine, soil moisture and fertilizer with forages, such as Festuca ovina and Agropyron cristatum, which results in a death of fine forages in large area. Control of the growth of poisonous plants was studied, and some measures were put forward for controlling the poisonous plants. Based on the carrying capacity of the natural grasslands, the theoretical grazing intensity was determined so as to provide the advantageous conditions for regenerating fine forages by reducing the number of livestock, implementing a rotational grazing system, and controlling the growth of poisonous plants.

Key words: natural grassland, poisonous plant, control measure, Urumqi County