Abstract: In a resonant grounded system, the accurate measurement of the system capacitance current is the basis of grounding fault arc suppression and protection. Therefore, the error analysis of the measurement method is very important. Aiming at the method of measuring the capacitance current of the resonant grounded system based on the transient information after the arc extinction, this paper studies the main factors including the current of the arc-suppression coil and the main resonant frequency after the arc extinction of the transient process which influence the measuring method, and analyzes the measurement error of the main resonant frequency via the graphical method of bivariate linear optimization, which is used to verify whether the measurement result of the system capacitance current meets the requirements of relevant standards and regulations. The results show that,considering the size of the resonant grounded system and on-site operation situation, the allowed measurement error of the main resonant frequency is recommended to take 0.100 Hz uniformly. The effectiveness of the error analysis method is verified through modeling simulation, and the method is also suitable for different system detuning degrees and different transition resistances,which has strong portability.