Abstract: What is Agricultural Engineering? Does it cover too wide a field to be attacked by research and planning? And what is it's relation with the other branches of engineering discipline? 10 years' practice of CSAE has answered these questions. The broadness and the comprehensiveness of Agricultural Engineering are determined by the nature of Agriculture. The important issues of land utilization, rural energy, protected farming or environmental engineering, and the application of remote sensing, computer technique and system engineering to Agriculture were discussed fruitfully in CSAE coferences in the past 10 years and not before. The close relation with biological nature of plants and animals and their products is another characteristic which distingr'shes Agricultural Engineering from other kinds of engineering. Agricultural Engineering is so important in rural development that it should put emphases not only to engineering design but also to economical and social considerations, so it is somewhat affiliated with social sciences. As such, Agricultural Engineering is not a duplicate of any other kind of engineering nor can it be replaced by any other kind of engineering. Agricultural engineers should cooperate with people of other disciplines to make ever better contributions to Chinese Agriculture which is now on it's way to modernization.