Currently, the power grid primarily employs a method that combines real-time monitoring with a wildfire trip-out model beneath the transmission lines for trip-out risk assessment. Although this relies on the real-time and reliability of satellite wildfire monitoring, there are still discrepancies between the actual wildfire combustion scenarios and the simulated environment of the trip-out model in some cases. To address the aforementioned issues, a full-process prediction method for transmission lines trip-out probability based on a wildfire spread model is proposed. Firstly, the forest fire spread model is utilized to predict the wildfire combustion state and flame boundary of the real-time monitored fire point, and the spatial position relationship between the transmission lines and the flame is obtained by combining the location information of nearby towers. Secondly, based on meteorological and wildfire spread conditions, the impact of flames and smoke on the insulation of transmission lines is analyzed. Finally, according to the analysis conclusions, the critical conditions for wildfire-induced insulation breakdown of transmission lines under different scenarios are established, and the classification calculation method for the trip-out probability of transmission lines due to wildfires is refined. This scheme combines wildfire spread characteristics with the dynamics of wildfire spread and transmission lines trip-out, addressing the deficiencies in existing wildfire prevention measures such as over-reliance on monitoring methods and discrepancies between actual combustion scenarios and model preset scenarios, thereby further enhancing the power grid's resilience to wildfire disasters.