As a kind of green water resources development, groundwater reservoirs have attracted more and more attention. However, phreatic water aquifer is only taken as object aquifer of most present groundwater reservoirs, research on confined groundwater reservoir is relatively poor. Quantitative research on influence of precipitation on confined groundwater reservoir regulation has become a research point for groundwater reservoir planning. Based on introduction to groundwater reservoir and its regulation and storage, quantitative research on influence of precipitation on deep groundwater reservoirs was made by using the numerical simulation method, with a groundwater reservoir in the west of Daqing as a study case. The results show that there is only a little influence of precipitation on the groundwater reservoir and average precipitation over years can be used in designing of confined groundwater reservoir regulation and storage model.