The transmission lines in southeast coastal areas of South China Power Grid are affected by typhoon and other gale weather all the year round. It is difficult to determine the actual anti-wind capacity of a large number of old transmission lines. The wind prevention and transformation of old lines has become an important task for disaster prevention and mitigation. In this paper，the evaluation method of wind energy reliability for transmission lines suitable for China is proposed by comparing with the evaluation regulations of wind energy reliability abroad，and the quantitative evaluation indexes are as follows： the anti-wind reliability of old transmissions lines can be characterized based on the reproduction period of maximum wind load that the structure can withstand，the maximum wind load that the structure can withstand is the largest wind load to satisfy the wind standard combination，different reproduction periods of the checking wind wind load can be calculated based on the 50-year baseline reproducible wind load multiplied by the reproduction period corresponding load factor.The paper gives the evaluation method of anti-wind capability based on reliability and puts forward the quantitative index，which make the evaluation and transformation of the transmission old lines in coastal areas more scientific and feasible.