Waveform　retracking　is　an　effective　method　to　improve　the　accuracy　of　sea　surface　height　measurement　with　the　satellite　altimetric　technique.　The　improved　threshold　retracking　algorithm　is　optimized　in　the　paper.　Several　waveform　retracking　algorithms　are　analyzed.　Then　a　waveform　retracking　system　is　programmed.　Several　retracking　methods　are　used　to　retrack　the　EnviSat　waveform　over　the　Mediterranean　Sea.　The　improved　threshold　retracking　algorithm　is　the　most　robust　retracking　method　and　more　suitable　for　the　EnviSat　waveform　retracking　over　the　coastal　Mediterranean.