The invention relates to a composite extractant used in a metal indium extraction process. The composite extractant is formed by mixing Bis(2-ethylhexyl)phosphate (P204), trioctylphosphine oxide and hexylphosphine oxide mixture liquid (C923) and trialkyphosphine oxides (TRPO) according to certain proportion. After being diluted with sulfonated kerosene, the composite extractant is used as an extractant used for metal indium extraction. The composite extractant has good chemical stability, good selectivity and high indium extraction efficiency which can achieve more than 90%, simultaneously can reduce the extractant emulsification, is easy for re-extraction, and the demand to extraction conditions of a system is not high.