In many scientific researches，people try tO discover the hidden relafionships among factors of some certain phenomena Most of these relationships can be expressed as functions．This paper analyzes the features of function expression and in．educes a function discovery method based on Gene Expression programming．The MEM method can deal with complex functions having n expressions(n>1)in difierent domains as well as those having only one uniform expression．The article also evaluates the complexity and performance of the method and shows that the MEM method has telarively low complexity due to the use of BDM algorithm and proves that the probabilityof successfulminingis 20％～80％，the averagetime elapsedislessthan 10s．