A novel triple-band microstrip patch rectenna was proposed for energy collection, and the receiving antenna was a new triple-band patch antenna with high gain. First, a U-shaped slot was etched on both sides of the patch to extend the path of the surface current; this ensured that the resonant frequency shifted to a low frequency and that the patch antenna was miniaturized. Second, by etching an H-slot and a U-slot on the rectangular patch, the current distribution was altered, and two new resonance frequencies were generated. The resonant frequencies of the antenna could be modified by adjusting the lengths of the H-slot and the inverted U-slot. The rectifier consisted of an impedance matching network, a rectifying diode, a pass-through filter, and a load. The two-stage matching network consisted of $\Pi$-type and T-type networks for matching the input impedance of the receiving antenna and the rectifying diode. A pass-through filter comprising a quarter-wavelength microstrip line and a filter capacitor was used to suppress high-order harmonics generated by diode nonlinearity in order to avoid energy loss. The receiving antenna and the rectifier were integrated as the rectenna. The experimental results show that, when the receiving power is approximately 3 dBm, the maximum efficiency of the rectenna is 54.1%, 43.9%, and 39.9% at 2.06, 3.43, and 5.25 GHz, respectively. Therefore, the rectenna can be used for the power supply of low-power electronic devices in the Internet of Things.