The available transmission capacity is one of the important indicators to reflect the safety and stability margin of the power system. With the development of intermittent energy and the randomness of the power system, the calculation of the probability of available transmission capacity has become the main direction of research in recent years. The article is based on the rapid development of wind power today, and the current probability of containing wind farms can be summarized by the research methods of transmission capacity. First, the definition of available transmission capacity is analyzed, and the definitions of various indicators for calculating the available transmission capacity are evaluated. Then, a series of uncertain factors in the power system containing wind farms are classified and discussed. Finally, the method of calculating the probability of using the transmission capacity is divided according to different principles. The steps, advantages and disadvantages of various methods are introduced respectively, and the advantages and disadvantages and practicability of various methods are summarized and forecasted. Finally, combined with the latest development requirements of the power system, the research direction of the probability of containing wind farms can be expected.