The south-north water project have been listed in the Tenth Five-Year Plan. Recently the east line and middle line in this project have been ready to start working. In order to change the status of lacking water in north of China, this paper discusses the necessity and the feasibility of diverting water from the southwest trunk rivers with the digital earth virtual technique, including the amount of water diverted, the geologic bedrock, the optimum line of diverting water and the impact on entironment.