Choosing a more reasonable vegetation index is critical to higher precision of appraisal of soil and water conservation. In this study，an experiment of twelve plots (5m×20m) was set up on the red soil hills in Changting of Fujian Province，South China. These plots were under two types of vegetation cover (pure forest and forest-grass) separately and had six levels of vegetation coverage (80%，60%，45%，30%，15% and 5%). Parameters of leaf area index (LAI)，vegetation fractional coverage (VFC)，rainfall，runoff and sediment were measured during the period of 2007 and 2008. Using the statistical analysis method，characteristics of soil erosion under different vegetation covers various in coverage in the region were studied，and soil erosion quantification by LAI and VFC was analyzed for stability and reliability. Results indicate that compared to the control plot，pure Pinus massoniana forest did decrease soil erosion modulus to a certain extent，but runoff insignificantly. In contrast，the mixture of forest-grass cut runoff by 25% and soil erosion modulus by up to 90%，suggesting that the vegetation fraction of forest-grass is more effective in soil and water conservation. The use of LAI to characterize soil erosion modulus under the two types of vegetation cover is able to reach the level of significance (P<0.05)，while the use of VFC is but only under the forest-grass cover. Therefore，it is advisable to choose LAI to characterize soil erosion modulus to evaluate soil and water conservation for more stable and reliable results.