Capacitive high-voltage bushing is one of the most important power equipment in substations, and their insulation status is very important for safe and stable operation of the power system. During the production and operation, insufficient drying or impregnation and ingress of external moisture may result in the humidified and unreliable insulation of bushings. Due to the particularity of the structure of the bushing, moisture is usually unevenly distributed in the capacitor core, especially in the case of external moisture intrusion. Therefore, a numerical simulation model of oil-paper-insulated double-unit laminated and 110 kV capacitor bushing is established. Frequency domain spectroscopy(FDS) characteristics under non-uniform moisture conditions are simulated. The results show that when the moisture is uneven, the tan δ-f curve shows obvious dielectric loss peaks. The frequency corresponding to the loss peaks goes up with the increase of the unevenness of moisture distribution. The FDS is sensitive to the insulation thickness and the moisture content in the final screen, and is basically not affected by the uneven axial moisture of the bushing.