Variable-pitched electric power plants are widely equipped and studied for their outstanding thrust response and preferable propulsion efficiency. Towards a typical variable- pitched electric power plant, this study presents an approach of degradation-tolerant onboard tuning. In order to improve the reliability of the power system model, the state variables of the power system are prevented from shifting due to battery degradation, Kalman filter and extended state observer based onboard tuning mechanism are proposed. Through the estimation of health information, the onboard model is properly tuned to satisfy practical requirement.