Abstract: An electrostatic detection and charge estimation method based on a four-probe array is proposed for online monitoring of abnormal particles in heavy-duty gas turbine gas paths. Four electrostatic probes are uniformly arranged around the pipe circumference to synchronously acquire induced signals generated by passing particles. A fused feature considering the output differences among probes is constructed to reduce the influence of particle spatial position on charge estimation. Using the charge measured by a Faraday cup as the reference, the relationship between the fused feature and particle charge is calibrated, and a charge estimation model is established. A high-temperature test platform is developed to evaluate the method under different temperatures, particle materials, and particle quantities. The results show that the method can extract transient electrostatic responses in high-temperature gas flow and realize particle identification and charge estimation. Non-metallic particles generally produce stronger electrostatic responses than metallic particles, while increasing temperature weakens the signal amplitude and increases background noise. The system can effectively identify 10 mg metallic particles, providing support for gas-path particle monitoring and early fault warning.