Abstract: This paper presents a numerical method for solving the two-dimensional long-wave equations given by [1],Since the method needn't treat the integral on the boundary, not only the amount of data preparations on the numerical computation is reduced, the computing, time is shortened, the computing error is lowered, but also the interference of the short-wave noise cited in [2] does not appear.The M₂ component tide in the Bohai Sea is calculated by the method give in this paper. It is more satisfacting that the calculated result coincided with the observed data.