This study intends to analyze the library classification of agriculture in DDC, from the Int edition to the 21th edition. Since Dewey Decimal Classification(DDC) was the first published in 1876, number of total items increased significantly a newly-organized and subdivision of them in the 8th, 10th and 12th edition. According as the discipline developed and was specialized, the agricultural division in DDC was fractionized, and new subjects were continuously added to it. After that time the first edition, the major changes arranged an class and order in the 15th and 17th edition. That is to say, ‘Farm economics’ in 631.1 was relocated to 338.1 in the 17th and ‘Veterinary sciences’ in 619 was relocated to 636.089 in the 15th. Especially, up to now ‘Farm Economics’ deals with an important branch in the science of agriculture. Here the matter of argue heatedly arranges it from economics to agriculture.