The present invention provides a kind of method of chemotherapeutic therapeutic effect for predicting colorectal cancer patients,The chemotherapy use contains α with molar ratio 1:0.5,α,The antitumor agent of α-trifluorothymidine and the chloro- 6- of 5- (1- (2- lminopyrrolidine base) methyl) uracil hydrochloride,The prediction technique includes following processes (1)~(2): (1) whether there is or not the processes of mutation for KRAS gene contained by the body sample that detection is acquired from the patient； (2) in the case that the result detected in above-mentioned operation (1) is that KRAS gene mutates,Predict the high process of a possibility that chemotherapy shows sufficient therapeutic effect to the what patient.本發明提供一種預測結腸直腸癌患者的化學療法的治療效果的方法，該化學療法使用以摩爾比1:0.5含有α,α,α-三氟胸苷和5-氯-6-(1-(2-亞氨基吡咯烷基）甲基）尿嘧啶鹽酸鹽的抗腫瘤劑，該預測方法包括下述工序(1)～(2):(1)檢測從該患者採集的機體試樣所含的KRAS基因有無突變的工序；和(2)在上述工序(1)中檢測的結果爲KRAS基因發生突變的情況下，預測該化學療法對於該患者顯示充分的治療效果的可能性高的工序。
