Abstract: Proceeding from the development process and present situation of Paddy Field Tillage Machines (PFTM) in Hunan recent years, this paper, using exponential smooth technology, forecasts the development tendency of PFTM during the eighth five-year plan in Hunan. Based on a vast amount of data collected and measured in Changsha area, the paper compares the benefit of PFTM with that of working animals, analyzes the size benefits of operations of PFTM and working animals, and studies the economic boundary of technical development of PFTM by means of economic benefit analysis for each of them instead of mathematical model. The analysis in the paper provides theoretic basis for popularization of PFTM in Hunan and other provinces in coming days.