This study is on the bamboo slips Geomancy complied by Peking University. The aim is to make a detailed analysis of its content, to verify its nature of divination and date selection, to clarify the main methods of its practice, and to get a general picture of it through literature review. The bamboo slips reveal that geomancy, as a method of date selection and divination from observing heavenly bodies and natural rules, was used to understand the laws of the Nature and human affairs. It is a scientific understanding of astronomy, astrology, and calendar systems. It exercises the knowledge of the heavenly stem and earthly branch and the five element systems. It corresponds with the principles of the changes of yin and yang and takes them as its basis. With the generating and overcoming theories of month names and the basic principles of the great encounter of yin and yang, it exhibits what is appropriate or inappropriate for a certain date or time and develops a divination system with the purpose of getting close to good fortune and avoiding bad luck