In this paper, a flexible Yagi-Uda antenna with polyimide substrate for wireless body area network (WBAN) is proposed. The prototype covers 2.45GHz Industrial, Scientific and Medical (ISM) band. The effects of bending along x-axis and y-axis for flexible Yagi-Uda antenna is analyzed. The resonant frequency, bandwidth and radiation patterns are simulated with various bending conditions. Results indicate that with increasing the bending degree, the input matching become worse. It is worth noting that the maximum radiation orientation at H-plane of endfire Yagi-Uda antenna deviates with bending along y-axis. The antenna prototype is fabricated with tested where the simulated results agree with the measured ones.