Abstract: The radar equation of dot type target and surface clutter ,and the calculation of receiver front terminal noise power is reviewed，and then three normally used empirical models of mean sea clutter reflectivity are introduced in detail. The characteristic of sea clutter reflectivity under different flight height and specifically sea status is analyzed by means of introduced empirical models. The trend consistency between the practical radar sea clutter echo and empirical models is compared and verified. The characteristic of the target detection in sea clutter is taken into account, then a fast method to analysis and estimation the flight height influence on the radar performance is given. The suggestion of flight height selection to maximize the air born surveillance radar performance is given in the end.