With the rapid development of China's UHV power grid,the future development trend is the interconnection of the regional power grid.However,in the early stage of UHV power grid construction,the electrical connection of the interconnected system is weak,and the tie-line stochastic power fluctuation limits its transmission capacity.In this paper,a calculation method of the fluctuation amplitude of the tie-line considering the stochastic fluctuation characteristics of load and wind power is proposed,the power fluctuation mechanism of the tie-line based on the frequency response characteristic is introduced,the probability distribution of wind power and load fluctuation is studied,and the method of estimating power amplitude for tie-line based on improved Latin hypercube sampling is proposed.The accuracy and validity of the proposed algorithm are verified by the example of North China-Central China interconnection system.