The efficiency of rainwater harvesting utilization plays an importantrole in a small rain-fed agricultural valley. With the Ankou Valley in Shandong Province as a study area, firstly, the influence of the soil infiltration on the rainwater collecting in a certain area was elucidated, rainwater harvesting efficiency was estimated by runoff coefficient method in hydrology. The experiment shows that the soil stabilization infiltration is less than normal, but the average runoff coefficient is 0. 46, higher than in Loess Plateau. So in such valley, it is much more advantage to develop rain-fed agriculture using the natural valley runoff area to collect rainwater.