The solvent countercurrent extraction process for total flavonoids from Toona sinensis (A Juss.) Roem leaves was optimized by orthogonal design. Using L16(45) orthogonal design, the experiments were conducted with extractive yield of total flavonoid as the major index and IC50 of scavenging DPPH free radicals of total flavonoid as the second index. The influences of the percent of ethanol volume, the ratio of material to liquid, extracting time, temperature and times on extracting yields of total flavonoids...