The design of an automatic water runoff monitoring field was outlined. It consisted of six runoff plots and a rainfall simulator, which was generally used to study erosive processes in sloping fields. A German-made surface runoff measuring device (Umwelt-Gerate-Technik GmbH, UGT) was used in this runoff field, which effectively improved sampling efficiency and reduced human error through automatic sampling and recording. The effect of straw cover on runoff processes and sediment yield on sloping fields was investigated using this runoff monitoring field. The results demonstrated that the straw cover could significantly decrease the rates of runoff and sediment deposition, and delay the onset of surface runoff and reduce the total amount of soil loss by 54.5%~63.8%. Maximum retention of plant residues as soil cover can effectively avoid sharp increases in runoff and limit water scouring effects. It is significant for alleviating soil erosion in sloping fields.