Abstract: In this paper, the instrument, principle and programm design of the computer graphic treatment for LED are presented in detail. Using this method and systems, the effective emission area for LED is measured accurately. The dependences of the injection current is or stripe width S and the half-full width W1/2 of the optical radiant intensity profile are calculated in theory. They well agree with the experimental measurement, and the accuracy of the experimental results are verified. A programme of graphic treatment is designed. The picture of the effective emission area, optical intensity three dimensional profile, and its equi-amplitude contours can be drawn. The longitudinal waveguid profile which is very useful in practice can also be calculated and drawn. Finally, the experimental results are discussed in detial.