Abstract: In order to understand effect of collecting agent and frothing agent on stability of three-phase clean coal froth in flotation,the primary slime of No. 9 coal sample from Shanxi Pangpangta coal preparation plant is studied by flotation test using four kinds of collecting agents and four kinds frothing agents,then the stability is determined by shaking method. The result shows that the stability is gradually improved as the concentration of collecting agent or frothing agent increases and will reach its maximum when agent concentration goes up to cut point,while the concentration continues to increase,it shows decline in stability. Moreover,interaction between collecting agent and frothing agent has a more complicated influence on stability of froth.