Ecosystem services are the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life. Soil conservation is one of the most important services, especially in the ecologically vulnerable region, Loess Plateau, which suffers from severe soil erosion for decades. A series of comprehensive controls of soil erosion have been carried out by the Chinese government to solve these problems. Surveys find that significant changes have happened in the land use pattern and the erosion control. Although some previous positive results have been achieved, large uncertainties still remain regarding the long-term policy effects on the vulnerable ecosystem in the future. Aiming at maintaining the sustainable ecosystem and economical development, keeping the low survival rate of trees, lightening the existence of the soil dry layers, and promoting economical development, it is necessary to evaluate the key ecosystem services including soil conservation on the Loess Plateau to quantify the comprehensive projects. It is also important because it can provide the support for the reasonable implementation of land use strategies, the soil conservation science and its technique research. Yangjuangou small watershed is chosen as our research area for its typical loess hill and gully topography of the Loess Plateau. Based on remote sensing data, GIS, and universal soil loss equation (USLE) model, we quantify the changes of the land use pattern and assess the value of the soil conservation in the small catchment from 1984 to 2009. Then, we develop four scenarios of different land use pattern to achieve the best composition of land use types and to discover the win-win scenarios of ecological and economical development. By calculating the amount of annual soil loss and simulating four scenarios, we get four main results as follows. (1) The land use pattern has been changed significantly from 1984 to 2009. The area of slope farm land and wilderness decrease with the area of forest and bush land increase respectively. (2) The soil conservation has been enhanced dramatically over these 25 years. The annual soil loss has declined from 21943.56 t/km2•a in 1984 to 8292.47 t/km2•a in 2009. Moreover, the soil erosion level of the main area falls down from the high erosion category in 1984 to the moderate erosion category. (3) The analysis of soil erosion in different land use types shows the value of soil conservation: forest>dam>orchard>bush land>young forest>terrace>grass land>resistant>slope farm land>wilderness. The study also focuses on the effects of slope changes on soil erosion, which finds that the soil conservation declines with the rise of slope levels. (4) Four scenarios of land use system, namely, main soil conservation benefit, main economical benefit, ecological and economical tradeoff and the sustainable coordination are put forward. The two former scenarios only achieved their ecological or economical benefit respectively without the integrated coordination development. The tradeoff scenario could balance the ecological and economical benefit, but it still faces a great risk of ecological security. The sustainable scenario is considered to be the best type because its stability of vegetation，the sustainability of economic and reasonable environmental polices during the global climate change period, although benefits of ecology and economy do not achieve their maximum value. Analysis on the scenarios of soil erosion indicates that the forth one can reduce or even prevent soil erosion, maintain or even improve the ecological security, and provide a win-win paradigm on the Loess Plateau. Our research addresses one methodology to measure the value of soil conservation, which can help to incorporate the value of ecosystem services and their interrelations into decisions with more sustainable strategies in the ecological vulnerable areas.