Abstract: This paper systematically analyzes the physical and chemical fields and their coupling in engineering geology. The fields are re-defined and the basic field concept is proposed accordingly to the engineering geological characteristics. The fields in engineering geology are classified as three categories, i.e. basic field, applied field and coupling field. Six fields are analyzed in detail. They are geological structural field, stress field, seepage field, temperature field, chemical field and deformation field. Then the categories of multi-field coupling are discussed and the multi-field coupling in engineering geology is studied. Finally the relative research topics are presented.