Sea Radar is an important technical measure for protecting national maritime resources and island sovereignty. The calculation of sea target velocity and course is important to monitor and track sea targets for sea radar, for calculation precision is directly related to the tracking effect of sea target. This paper systematically studies the problem on calculation of sea target velocity and course for sea radar, explicates the relevant technical principles, proposes effective algorithms for calculating sea target velocity and course based on multi-frame accumulative information, and gives a corresponding solution suitable for the scenario of sea target maneuvering. Finally, based on comparison analysis of real radar data and Automatic Identification System (AIS) data, we verify the precision of our algorithms.