Osmotic method was based on the principle of moving some water out of food by soaking the food pieces in solution concentration higher or the water activity (aw) under the food. The difference between osmotic pressure of aqueous solution the food causing the propulsion (driving force), which caused the mass transfer between each stripe osmotic substances and food. By the spread of the water from the slices of food through the cell membrane into a solution. And at the same time, the spread of solid from a solution through a membrane into a piece of food. In addition, the potential spread of organic acids, vitamins, natural substances proven out cells in small quantities. Imported sugar and salt to prepare an osmotic solution widely. Because there are many advantages such as a high solubility was a good performance to pull out a piece of food, water and improve the taste of food after osmosis equipment. To understand the behavior of the mass transfer of osmosis by which this research, experiments with sweet potato and used as baseline data to develop.