The present invention provides a method of evaluating drug resistance in hormone therapy including the following steps. Firstly, a primary level of TRBP in a subject is measured, and an effective amount of tamoxifen, an active form of tamoxifen or an analogous of tamoxifen is provided to the subject. Then, a level of TRBP in the subject is measured after providing tamoxifen, the active form of tamoxifen or the analogous of tamoxifen. Finally, a level change of TRBP in the subject is discriminated to determine a tamoxifen resistance.