Smoothing and filtering two-dimensional sequences are fundamental tasks in fields such as computer vision. Conventional filtering algorithms often rely on the selection of the filtering window, limiting their applicability in certain scenarios. To this end, we propose a novel Two-Dimensional Smoothing (TDS) algorithm for the smoothing and filtering problem of two-dimensional sequences. Typically, the TDS algorithm does not require assumptions about the type of noise distribution. It is simple and easy to implement compared to conventional filtering methods, such as 2D adaptive Wiener filtering and Gaussian filtering. The TDS algorithm can effectively extract the trend contained in the two-dimensional sequence and reduce the influence of noise on the data by adjusting only a single parameter. In this work, unlike existing algorithms that depend on the filtering window, we introduce a loss function, where the trend sequence is identified as the solution when this loss function takes a minimum value. Therefore, within the framework of the TDS algorithm, a general two-dimensional sequence can be innovatively decomposed into a trend sequence and a fluctuation sequence, in which the trend sequence contains the main features of the sequence and the fluctuation sequence contains the detailed features or noise interference of the sequence. To ensure the reliability of the TDS algorithm, a crucial lemma is first established, indicating that the trend sequence and fluctuation sequence obtained by the TDS algorithm are existent and unique when the global smoothing parameter is determined. Three modified algorithms are then proposed based on the TDS algorithm, with corresponding lemmas and corollaries demonstrating their reliability. Finally, the accuracy and effectiveness of the TDS algorithm are further verified through numerical simulations and image processing cases.