The estimation of citrus yield is important to citrus precision management. Fast non-destroyed measure could be achieved using machine vision technology. Ten images of citrus were used in this experiment and yield of each tree was measured in advance. The citrus image was segmented based on the RGB color model. The segment condition for citrus and background is: (R-B>100) & (R>G). The total number, the total perimeter and total area of citrus were computed from the segmented image. The relationship between each image parameter and citrus yield was analysis. The result of experiment shows that the correlation coefficient between the total citrus number and the yield of citrus is 0.97 and indicates that it is has good prospect in the future.