###### Abstract
For the coastal 'contamination', strong reflections on the coastal sea surface leave a hyperbolic trajectory through waveform space, and there is a geometric relationship between the reflections and sample gates of the waveform [17; 18], which gives the physical possibility to position the distorted part of coastal waveform. Simply comparing along-track echograms from different satellite data of the same spatial-temporal area, some objects called 'bright targets' on the sea surface can be estimated using geometric analysis [19]. Furthermore, according to the relative location of coastal 'pollution' in relation to the satellite nadir, the corresponding waveform noise is removed from the along-track echograms, and along-track waveforms with clean trailing edges are obtained [20]. When the distortions of the waveform are irregular and fragmentary, the waveform distortion parts can be detected directly by the shape characteristic. Multiple Brown-peak (MBP) waveform retracking uses adaptive peak detection (APD) to recognize the peak noise of the Brown-peak waveform and processes the distorted trailing edge of a single waveform efficiently [21; 22]. Furthermore, the shape classification of coastal waveform can improve the efficiency of waveform retracking algorithms, which is the initial step for coastal waveform retracking process systems [23; 24; 25]. The advantage of waveform classification is that it solves the problem of a single waveform retracking strategy being unable to process all coastal waveforms with the same precision. Based on the a priori knowledge of different waveform retracking algorithms, coastal waveforms are divided appropriately into several types and can be processed to maximally improve the quality of the data. However, it is necessary to comprehensively consider the fitting-deviation between different waveform retracking strategies [21; 26]. In short, the quality of coastal altimetry data has been greatly improved. Accurate observation extends to a range of approximately 5 km offshore thanks to the development of coastal waveform retracking. For most coastal waveform retracking strategies, the judgment of a coastal waveform is a credible leading edge and a terrible trailing edge. The influence of coastal 'pollution' on the leading edge of the waveform is ignored, and the effective trailing edge information is not considered adequately, which contributes to recovering accurate coastal altimetry observations. The HY-2A satellite equipped with a radar altimeter, as the first Chinese marine dynamic environmental satellite, was launched in 2011. Subsequently, HY-2B, HY-2C and HY-2D were successfully launched in 2018, 2020, and 2021, respectively, forming a marine dynamic environment-monitoring satellite constellation. Currently, HY-2B, HY-2C, and HY-2D are in orbit, providing high-quality observation data for ocean scientific research and monitoring. The accuracy of HY-2B satellite coastal altimetry data is always lower than that in the open ocean due to the inapplicability of the MLE4 retracker in coastal areas, limiting the application of the HY-2B data product in the coastal area. In this study, a coastal waveform retracking strategy for HY-2B satellite altimetry is proposed. By intercepting the leading edge of the waveform with less noise and confirming the effective part of the trailing edge, accurate estimations of coastal waveforms can be recovered. In addition, the coastal waveform retracking strategy proposed in this study prevents waveform classification and the boundary dividing for open ocean and coastal areas and has good performance both in open and coastal sea areas. The data accuracy and reliability of HY-2B altimeter data within the range of approximately 0-15 km offshore are greatly improved. The study areas and the HY-2B altimetry data used are introduced in Section 2. Section 3 introduces the waveform models and the coastal waveform retracking strategy proposed in this study. The waveform retracking results of the coastal HY-2B altimetry data are presented in Section 4.