The agricultural structure is defined as an interactive combination of controllable factors which constitutes a supporting framework of the agricultural system. It is a dynamic structure which changes with economic development. In the process of agricultural modernization changes of agricultural structure include following aspects:1. Extending industrial chain with in agricultural system and developing pre-and post productive sectors.2. Changing input structure and substituting land and labour with capital and technical investment.3. Changing management and organization structure. including changing tenure system. enlarging farm scale. improving agricultural service. developing regional and professional cooperatives and agricultural-industrial-commercial integration etc.4. Rationalizing sectoral structure and areal specialization of agricultural production.5. Developing agricuhural infrastructure and improving circulation and market system of agricultural products.Currently in China. the traditional agriculture is gradually transforming into the modern one and the changing agricultural structure attracts attention of many experts from different disciplines.The authors of this article suggest that geographers should actively take part in the studies of agricultural structural changes. and the concept of " major agricultural system" should be accepted for the purpose of expanding the area of their scientific investigation. encouraging theoretical innovation. improving reseach methods and techniques.and serving the agricultural modernization.