A double-skinned composite tubular (DSCT) offshore wind power tower was proposed and automatic section design software was developed. The developed software adopted a nonlinear material and nonlinear column model. As long as the outer diameter, material properties, and requested capacities are known for the DSCT wind power tower, the developed software can perform axial force-bending moment-interaction analyses for hundreds of sections of the tower, as well as suggest ten optimized cross-sectional designs. Assuming that the inner and outer tubes were made of steel, the software performed experimental design processes for a 5.0 MW and a 3.6 MW turbine. The software suggested rational and satisfactory section designs, and showed the possibility of a DSCT tower being used as an offshore wind power tower.