The previous study indicates that both reagent usage and the variation of water conductivity affect froth stability and therefore coal flotation behavior. In this study, Central Composite Rotatable Design (CCRD) was conducted to investigate the interaction 1 of saline water with collector (diesel) and frother (MIBC) in controlling froth stability which was indicated by air recovery. The results show that a significant interaction 1 existed between flotation reagents and water conductivity, which affected froth stability, combustible mater recovery and the mineral matter content of flotation concentrate. Frother and salt ions had a joint action in producing a more stable froth. On the other hand, collector and salt ions had a joint action in reducing the combustible matter content of flotation concentrate and the combustible matter recovery. A 1 A term in statistics meaning that the effect of two or more variables is not simply additive.