In order to fully tap the transmission potential of transmission lines, it is necessary to use the Dynamic Line Rating (DLR) of transmission lines. Due to the timeliness of power grid decision-making, EMD-BiLSTM-BO model and Recursive multi-step forecast strategy are combined to complete the day ahead forecast of micro meteorology. Considering the cumulative error from recursive multi-step forecast strategy, the Gauss Distribution model is established based on the forecast error, which used to conservative micrometeorological parameters. Furthermore, the Arrhenius-Weibull model is established to simulate the aging damage of wire due to long-term working in high temperature environment. A case result of XIANMENG II 500kV transmission line in Central China show that, power grid managers can use DLR proposed in this paper to dynamically adjust transmission line current to greatly tap the transmission potential of existing transmission lines on the premise of ensuring safety and reliability.