The purpose of this study is to enhance the accuracy of numerical wave forecast with data assimilation. A technique - spectral data assimilation combine model results with measured data. Using measured data to correct model results immediately and then to do wave forecast. We adopt sequential data assimilation to do data assimilation. In the process of data assimilation, the optimal interpolation of partition from Voorrips, etc. is adopted and improved. And the analytic data is from data buoy. Expect to set up the technique of spectral data assimilation. And then discuss the result which using spectral data assimilation to typhoon numerical wave model in order to verify the accuracy of spectral data assimilation model and analyze the wave character Taiwan water.