Abstract: In order to reinforce the nutritive medium management and to recycle the nutritive medium in greenhouse culture, it is required to measure the value of EC, pH and the content of nutrients on line, thus adjust every ingredient to equilibrium in time. In this paper, application of ion selective electrode implements the on line measurement of some ingredients, such as the concentrations of ions of Nitrogen, Kalium, and Calcium, EC and pH, and implements the soft sense of the concentrations of ions of Phosphorus, Sulfur and Magnesium according to the relative stable relation of concentrations of every ingredient and the value of EC, pH in a period when growth circumstance is relatively stable for special crop in special growing period, as well as the relation among variation of every ingredient.