Abstract: p tert butylcalix8 arene octacarboxylic acid (H 8L) has been synthesized. The solvent extraction of Fe 3+ and La 3+ with above calixarine is carried out under the condition of (30±1)℃, I =0 1 mol/kg. It is found that H 8L has a good extraction ability towards Fe 3+ and La 3+ with the order of Fe 3+ ,La 3+ . By the slope method, the extraction mechanisms are given out as follows: Fe 3+ +H n L (o) FeH n -3 L (o) +3H +(lg K ex =-3 28±0 03) and La 3+ +H n L (o) (LaH n -1 L) 2+ (o) +H +(lg K ex =1 28±0 06). In the presence of Na + and K + in the aqueous phase, sodium and potassium ions have participated in the extraction process of La 3+ , the composition of intermediate complex is H n -1 5 LKNa 0 5 .