Most of advanced colorectal cancer will progress after first-line treatment; therefore, seeking an efficient and low toxic maintaining regimen to prolong PFS becomes a hot topic in oncologic field. Some clinical researches demonstrated that maintaining treatment followed first-line treating advanced NSCLC could extend PFS and OS. In metastatic colorectal cancer, patients receiving 5-FU/leucovorin(LV) maintaining therapy experienced significantly longer PFS than that stopped chemotherapy after six cycles of FOLFOX4 in OPTIMOX2 study. One phase II study shown that median PFS was 13.9 months, and median OS was 31 months in 30 patients receiving first-line treatment of six- month FOLFOX4 followed by UFT as maintaining treatment . A non-randomized small sample study conducted in department of medical oncology of Sun Yat-Sen University Cancer Center indicated that patients receiving first-line treatment of XELOX followed by capecitabine as maintaining therapy has significantly prolonged median TTP, comparing with the non-maintaining treatment patients,(14months vs. 9 month, respectively).