Abstract: How to generate and anti-aliased draw circles is an important problem of computer graphics.In order to improve the circle-drawing speed, a basic circle generating algorithm is presented.In the algorithm, residuals rather than intermediate data are used as decision parameters, the addition of constant in every loop is eliminated.Since grey conversion can be obtained in a simple manner, the algorithm may be easily developed into an integral anti-aliased algorithm.Two algorithms are constructed by quite similar structure, and are all more effective than other algorithms.By calculating and drawing slices one by one with double-step technique, the developed run-length algorithm can effectively increase the circle-drawing speed due to the great reduction of operations.The experiment results prove that the circle-drawing speed of the run-length algorithm can be almost 1.7 times comparing with that of basic algorithm.