Abstract: In response to the practical problems of insufficient reliability of high-voltage switchgear and inaccurate life assessment under the background of high short-circuit capacity and frequent reclosing operations in urban power grids, this article proposes an integrated method consisting of multi-physical field coupling optimization, full life cycle Bayesian life assessment, and graded status warning. At the design end, an electro-thermal coupling model is established to correlate contact temperature rise, contact wear, and insulation margin, and a Cu-W substitution and heat dissipation fin scheme are provided; at assessment end, a degradation latent variable network is constructed based on factory tests, online monitoring, and maintenance records to achieve predictive rolling remaining life estimation and prior reset of maintenance intervention; at operation end, a preventive maintenance strategy with hysteresis threshold is formed and closed-loop feedback is implemented. The application of method in 10 SF6 circuit breakers of 3 220 kV substations shows that the unplanned outage frequency has decreased from 3 times per year to 0.5 times per year, average maintenance cost has dropped from 400,000 yuan per unit per year to 300,000 yuan per unit per year, and the accuracy of remaining life prediction has increased from 80% to 92%, verifying comprehensive benefits of scheme in terms of reliability, economy, and implementability.