This study mainly describes the fractal property of the frequency spectrum of the sea clutter and the application of the obtained fractal characteristic in frequency domain to the constant-false-alarm-rate (CFAR) target detection within sea clutter. First, this study takes fractional Brownian motion (FBM) for example, and the spectrum of the FBM is proved to be fractal theoretically on condition that the time series of the FBM is fractal. This argument lays the foundation for the application of