This work shows the extraction of cesium (Cs +)and rubidium (Rb +)from salt lake brine containing potassium (K +)and magnesium (Mg2 +). The results show that 4 - tert - butyl - 2 -(α -methylbenzyl)phenol (t - BAMBP)diluted in sulfonated kerosene (SK)has an excellent extraction effect. Infrared spectroscopic studies indicate that polymerize to form the dimer in the t - BAMBP when Cs + or Rb + were extracted. The effects of K +,Mg2 +,t - BAMBP concentration,the volume ratio of organic phase to aqueous phase (O/ A)and the alkalinity (pH)of aqueous phase were investigated. The K + and Mg2 + should be eliminated through precipitating before the extraction and separation of Cs +and Rb + . The optimum extraction conditions of the experimental brine were as follows:0. 8 mol/ L t -BAMBP diluted in SK,pH≥13,a phase ratio of 1:1,and an extraction contact time of 2 min at room temperature. The optimal extraction yields of Cs + and Rb + were as high as 100％ and 85. 8％,in addi-tion,8. 76％ of K + was co-extracted. Further work would increase the extraction yield and selectivity of Rb + and realize the efficient separation of Cs + and Rb + from brine.