Overspeed events may occur in the operation of aero-engines， which may lead to hazardous engine consequences of “uncontained high-energy debris”. Based on the safety requirements of aero-engine airworthiness certification for overspeed events， this paper analyzes the requirements of electronic overspeed protection system for a new type of sensors. We analyze the measured signals of the exploratory test of exhaust electrostatic monitoring of a certain type of aero-turboshaft engine. The analysis results show that the spectrum information of the electrostatic sensor signal can dynamically track the rotor speed in real time. The power turbine speed between 170—180 Hz and its doubling frequency are identified in the spectrum information under six output shaft power conditions of 75， 210， 420， 630， 840 and 1 000 kW. The obtained results demonstrate that electrostatic sensor has potential applications in aero-engine overspeed monitoring.