Several problems related to the three-dimensional volume rendering from sector scanning images have been deeply studied in this paper. To counter the key problem that the points on the two adjacent images are not same interval, the recursive interpolation algorithm for the unequal interval, by which the data changes continuously and gradually, has been put forward in this paper. Therefore, the problem, how to make interpolation amid the unequal interval in the volume rendering from sector scanning images, has been well solved. Besides, the formation of outer curved layer volume is another key problem in the volume rendering from sector scanning images. The algorithm based on cubic parameter spline function for forming the outer curved layer volume has been proposed in this paper as well. Using this algorithm, the smooth outer surface can be obtained. On the basis of unparalleled two-dimensional section images, the three-dimension reconstruction from sector scanning has been firstly realized using volume rendering. And, several tested images of irregular model from sector scanning are presented. The tested results indicate that the algorithms presented in this paper are correct and practicable. The effect of reconstructed images is satisfactory.