Abstract: The synergistic effects of combined reagents have been investigated using the application of the flotation reagents theory and the physicochemical properties of surfactants. Taking some combined reagents such as oleic acid and carboxylic acid with different carbon chain length,sodium oleate and carboxylic acid with different saturation，emulsifier and sodium oleate，sulfonate and sodium oleate，carboxylic acid and benzohydroxamic acid，for example，through the calculation of agent structure parameters and interaction of hydrophobic chain/hydrophobic chain，and compared with literature data，it is found that the combined reagent with large difference in agent structure parameter，surface tension descending significantly，strong interaction of hydrophobic chain/hydrophobic chain，and strong selectivity and collecting ability performs better in flotation. This paper has theoretical refevences significance on quantitative research of combined reagents synergistic effects.

Key words: Combined reagents, Synergistic effect, Structure and property, Surface tension, Flotation