Abstract: Morphology imaging as a traditional method to evaluate the therapeutic effect of malignant tumor, needs to much time and can't reflect the biological changes. So it is replaced by molecular imaging method gradually. ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET imaging shows remarkable merit in the diagnosis, staging diagnosis and effcet monitoring of many kinds of tumor, but its specificity is low. So it can't evaluate the therapeutic effect accurately. Studies show that the prospect of ¹⁸F-fluorothymidine PET imaging is to monitor the therapeutic effect of malignant tumor, and is better than that of ¹⁸F-FDG.