Abstract: The economic indicator of a drilling mast or derrick made in China is higher than that of the same type made in other countries. Formulas for the optimized structural design of a drilling mast or derrick with given the structural topology and geometry are derived in the paper. The objective is to maximize the economic indicator of the structure with the drilling uzast or derrick simplified as a space frame. The constraints considered include local buckling constraints of members and overall buckling constraints of the structures in addition to the usual stress, member size and displacement constraints. A computer program is also worked out in the paper. One example is given and one existing mast is computed in contrast with its original design. It is pointed out that local and overall buckling constraints must be taken into consideration.