In this preseantation, farm budget analysis is described as a tool to understand economic performance of agriculture practice - to assess impact of technology intervention and price and policy changes. This helps better understand strengths and weaknesses of various farm operations. As a type of farm budget analysis, the farming system modeling software "Olympe" developed by a consortium of INRA/CIRAD/IAMM, is an efficient software to analyze and model farming systems performance. Olympe enables a comprehensive overview of farmer situation and links to technical innovations and practices. A range of analyses can be carried out such as the economic impact of technical choice, effect of climatic or economic uncertainty as well as the environmental impact of land use options. Conference paper on this presentation is held in the Mounatin Forum on-line library.