This paper presents the design of wireless power transmission circuit on a small planar wide-band antenna. The proposed rectifying circuit consists of a microstrip line, a Schottky detector diode and a capacitor. Our proposed rectifying circuit can work at 2.45 GHz, 3.8 GHz and 5.8 GHz, namely, multiband operation, and circuit size is 56 mm × 43 mm × 1.6 mm. The proposed small planar wide-band antenna has a maximum gain of 1.26 dBi at 2.5 GHz, 0.37 dBi at 3.8 GHz and 3.32 dBi at 5.8 GHz. The maximum conversion efficiencies of this circuit achieved at free space are 26.8%, 29% and 43.3% at 2.5, 3.5 and 5.8 GHz with load resistances of 2000, 510, 1300 and 0 dBm input power level.