Abstract: The investigation and study in Shanxi Province shows that grain yield on dry field is restricted by soil moisture in the driest grow period of crop, and the agricultural yield seems to be of the “double hoopedbarrel effect”.　The double hoopedbarrel effect indicates there is still great potentiality of water to be exploited in dry field,for this,the technological countermeasures are proposed in this paper: For those regions where there are no other water resources,based upon local annual total precipitation, the catchment area being regarded as the irrigated area again, partial precipitation in peak period can be collected and stored properly on the spot, which will be used to irrigate crop effectively in the driest growth period so as to obtain relatively high and steady yield. As the water catchment field and the irrigated area is the same area, this kind of irrigation technique is called “OntheSpot Irrigation with Rainwater Collected from the Same Cultivated Field” and “OntheSpot Irrigation” for short.It is estimated that the onthespot irrigation may be both a gap of increasing of grain output and a stragetical measure of solving the problem of the shortage of water resources.