The article proposes a wideband injection-locked frequency tripler （ILFT）. Based on the conventional injection method， the tripler used a push-push differential pair to double the frequency of the input signal and coupled the generated second harmonic to the source common mode node of the injectors through a transformer， which enhanced the second harmonic at the source common mode node of the injectors. Since the injection current is generated by mixing the injected signal with the second harmonic at the source common mode node， the injection current is also enhanced， thereby increasing the locking range. In addition， the tripler adopted a fourth-order resonator， as a result， the phase of the resonant impedance is flattened at the zero-crossing point， then the locking range is further increased. The tripler is implemented in a standard CMOS 65-nm process with a chip area of 720×670 μm²， and the power consumption is 15.2 mW under a 1.2-V power supply. With 0 dBm power injection， the locking range is 19.2-27.6 GHz， the corresponding fundamental suppression ratio is greater than 25 dB， and the second harmonic counterpart is beyond 35 dB. The proposed ILFT is capable of the requirements of the oscillation source of the 5G transceiver.