Abstract: In recent half a century for the Tibet, soil nutrient in farmland showed a serious degradation due to dramatically decreased usage of soil organic fertilizer; the difference in farming management system and seldom maintenance to the cultivated land by farmers and herdsmen, for 76% of arable land lack of effective nutrient content and discordant among fertility factors. It was reported that soil organic matter content reduced to 2% for more than half of the farmland since the 1960s, the scale of decrease was 26.7%~52.0% for soil organic matter content in main grain –growing areas of farmland only in ten years of 1990-2001. Soil organic matter content in farmland showed a decreased dramatically which leaded to declining of soil fertility in farmland and reducing of soil permeability and water conservation capacity. The soil organic matter in farmland of Tibet should be both taken a general investigation and conducted a lucubrate in the conversion, For the purpose of increasing soil organic matter content , reducing the soil fertility degradation speed, the following suggestions should be adopted: Increasing usage of organic fertilizer and planting green manure.