Abstract: When the ultra high frequency (UHF) sensor is adopted to test the partial discharge inception voltage(PDIV) of the motor insulation system, the existing UHF sensors are mostly rigid base antennas with large volume, and the test position is more restrictive. This paper designs a flexible narrow-band antenna that can be attached to the motor stator. By flexibly changing the test position, the PDIV of the motor stator insulation system can be sensitively detected. The total thickness of the designed antenna is 0.16 mm, and the size is 90 mm×100 mm. Through simulation and measurement analysis, it is found that when the antenna bending curvature radius changes from 1.5916 mm to 11 cm, the resonance frequency point shifts to the right, and its operating frequency band is at least 0.7~1.2 GHz. A motor stator insulation partial discharge(PD) detection platform is built to analyze the antenna performance. The experiment shows that, compared with the external Archimedean spiral antenna(ASA), the built-in flexible antenna has higher sensitivity, and the received PDIV signal amplitude is at least 100 times that of the external antenna. The frequency domain is distributed from 0.2 to 1.1 GHz. The experiment also shows that the detection sensitivity of the different attachment positions of the flexible antenna is ranked from high to low: the motor end, the inner wall, and the outer wall. Attaching the flexible antenna to the outer wall of the motor can avoid damaging the motor structure while detecting the PD signal generated by the insulation of the motor offline experiment or online operation.