The characteristics of cofferdam and foundation pit were analyzed. On this basis, the concept of seepage field regulation was put forward for cofferdam and foundation pit. The regulation aims at safety, construction period and cost control, as well as environment protection. It is emphasized that the efficiency can only be guaranteed by adequate and proper regulation measures at the right moment. The regulation measures were classified as preinstalled and urgent ones according to the time to take. Pertinent regulation measures and application conditions were presented. Furthermore, the importance of urgent measures when preinstalled measures failed was illustrated by an engineering example. The dynamic characteristics of seepage field corresponding to many factors were taken account into the seepage field regulation theory. With this theory, prompt and effective regulation measures would be arranged and fulfilled in the whole process through work planning, construction and operation to achieve aims inclusive of guaranteeing engineering safety, controlling construction period and cost, and mitigating negative effects on environment. Seepage field regulation theory is significant for all engineering involving surface and subsurface water.