Electric-field-based stimulation is emerging as a new cancer therapeutic modality through interfering with cell mitosis. To address its limitations of complicated wire connections, bulky devices, and coarse spatial resolution, an improved and alternative method is proposed for wirelessly delivering electrical stimulation into tumor tissues through designing an implantable, biodegradable, and wirelessly controlled therapeutic triboelectric nanogenerator (ET-TENG). With the excitation of ultrasound (US) to the ET-TENG, the implanted ET-TENG can generate an alternating current voltage and concurrently release the loaded anti-mitotic drugs into tumor tissues, which synergistically disrupts the assembly of microtubules and filament actins, induces cell cycle arrest, and finally enhances cell death. With the assistance of US, the device can be completely degraded after the therapy, getting free of a secondary surgical extraction. The device can not only work around those unresectable tumors, but also provides a new application of wireless electric field in cancer therapy.