[Background] In recent decades, soil erosion has become severe environment problem in southwest Yunnan with the increasing of young orchard. Soil erosion is a complex process that depends on soil properties, ground slope, egetation, and rainfall amount and intensity. Due to the exceptional weather and geographical conditions, the situation is more special in southwest Yunnan. Therefore, it is a critical issue that how the soil and water runoff and degradation of orchards is controlled in this area. This field study aimed to explore the effect and mechanism of soil and water conservation by different tillage practices. [Methods] The field trails were conducted on a red soil sloping land at Baoshan with altitude of 2 300 m. Long-term average annual rainfall is 966.5 mm and annual temperature is 15.5 ℃ at this site. A total of 3 treatments (traditional tillage, straw mulching, and biological covering) were set up, each treatment was repeated for 3 times, and the area of each treatment was 30 m². Plum was cultivated with plants spacing of 10 cm and row spacing of 30 cm at all treatments. Different treatments were applied on the spacing between rows: not planting any crops, mulching corn straw, and inter-planting mixed grasses. Soil nutrition content (nitrogen, phosphorus, and potassium), surface runoff and soil loss amount were determined by the process of study. [Results] After a 2-year trial, soil organic matter, total nitrogen and total potassium contents increased by more than 14%, runoff amounts reduced by about 20%, erosion reduced by 10% -30%, losses of total nutrient decreased by 20% -30% when compared with traditional tillage practice, and the effect was more significant in biological covering tillage. The results from the study showed: 1) Tillage with biological covering resulted in a slight increase of soil porosity and reduction of bulk density. 2) Both treatments resulted in the reduction of soil loss and soil nutrient loss. The percent of decrease in runoff by biological covering was 18.1% in the first year and 26.3% in the second year when compared with raditional tillage, while 19.5% and a slight increase respectively in those two years by straw mulching. Soil erosion showed the same tendency, 17.5% and 26.6% by biological covering whilst 19.0% and 0.5% by straw mulching for the past two years. 3) With the experimental time advancing, the runoff amount and soil erosion of the biological covering treatment presented a declining trend, while which of the straw mulching increasing. The percent of decrease in soil loss by biological covering and straw mulching was 10.0% -13.5% for the first year and 27.1% -29.2% for the second year when compared with traditional treatment. Soil nutrient loss showed the same tendency, 20.5% and 32.2% for each year. [Conclusions] Therefore, both straw mulching and biological covering improved soil nutrient status and reduced soil erosion, and biological covering showed more obvious influence. Moreover, the effect of soil and water retention became more significant with the advance of study time under the practices of straw mulching and biological covering.