Abstract: Concept of dimension has been generally used both in natural science and humanities among modern scientific system. Dimension owns its reality of theoretic system and is one part of scientific framework. Pratacultural science has four dimensions where Grassland Typology, Grassland Ecological Chemistry, Grassland Agro-ecology and Pratacultural Information System constitutes typological dimension, chemical dimension, systematic dimension and information dimension, respectively. Typological dimension plays a key role in cognition of grassland phenomena, chemical dimension is primary indicator of ecological efficiency and economic efficiency of pratacultural system, systematic dimension maintains the existence and continuation of modern pratacultural industry and Pratacultural science and information dimension forms the ‘neural networks’ of modern Pratacultural science. Every dimensional subject has the distinctive and whole theory system whilst four dimensional subjects infiltrate mutually and develop crosswise, which is expressed in three knowledge sectors and the other subjects of Pratacultural science. In this way, dimensional subjects integrate and condense Pratacultural science and hence produce the multi-dimensional structure with high ecosystem diversity.