A study with 10 treatments was conducted in the long-term observation station of the South Xiaohegou watershed to investigate the law of soil and water loss under different surface treatments. Results show that soil loss was not consistent with runoff processes, but affected by slope. The soil loss incremental rate generally increased with increasing slope degree. However, when slope increased, slope length for collecting the same amount of water as at the smaller slope increased, which could lead to a reduction in water infiltration into soil, but the total infiltration increased. Therefore, runoff amount did not show a proportional increase with slope increase when slope was greater than 20°which was determined as the threshold. The study also shows that a mixed plantation of Chinese pine tree with sea-buckthorn at a coverage of 65% could significantly reduce soil and water loss, with a sediment concentration of 2.377 kg/m³ which was 57.77% lower than soil loss on the bare land. The averaged runoff of 0.121 m³ under the plantation was 19.74% lower than the bare land. In 2012, soil erosion index for the Yangjiagou watershed where biological control practices for soil and water conservation had been applied was 2 589.95 t/km² lower than the Dongzhuanggou watershed which remained in the natural conditions without any human disturbance.