Abstract: In order to calculate the absorption efficiency of different doubleclad optical fibers, twodimensional analysis, threedimensional analysis and fiber optics wave coupling theory were adopted in the past. A 3-D method based on Zemax software was introduced in this paper, the absorption efficiency of circular, offset, rectangular, D-shape, octagonal double-clad fibers were investigated by writing ZPL macros, and the results were compared with the data obtained from the 2-D analysis. Data showed that two results were similar and the absorption efficiency trends of different inner-clad fibers were same. The solution based on Zemax had many advantages in comparison with the 2-D analysis. The simulation based on Zemax was more vivid because the relationship between the absorption efficiency and fiber length could be achieved, however, the relationship between the absorption efficiency and reflection times was obtained based on the 2-D analysis. The critical angle could be set in Zemax, rays with arbitrary angle were emitted from the arbitrary point in the inner-clad section in the 2-D analysis ignoring ray total reflection condition in the inner-clad, so the result based on Zemax was more accurate. It was easy to simulate the different inner-clad shapes and the non-sequential ray tracing velocity was very fast, the operation time based on Zemax was 373 seconds, and was 1 732 seconds based on 2-D analysis under the same condition for the same rectangular inner-clad fiber,so the calculate speed based on Zemax was more rapid. The absorption efficiency of a new structure double-clad fiber put forward by professor LOU Qi-hong was calculated finally.