Most of the rated capacity design of transmission lines is based on conservative meteorological conditions such as high temperature and low wind speed, and the rated capacity is a fixed value. This conservative method often leads to insufficient utilization of line capacity. The method of dynamically adjusting the line capacity is to adaptively calculate the available capacity of the line by using the local meteorological parameters such as wind direction and wind speed and the grid load. In this paper, the local wind field is modeled based on hydrodynamics calculation, and the wind field modeling results are combined with the meteorological station data to estimate the available capacity of the line. The proposed method is tested on overhead lines in Shenyang suburb. The results show that the calculated available capacity is higher than the static rated capacity in 76% of the research time, and it is 22% higher than the static rated capacity, which verifies the effectiveness of the proposed method.