When designing a serial robotic arm based spatial pointing mechanism, a challenging problem is to identify all the design variables to satisfy all the requirements of launching, working conditions and adjustment of working state. Traditionally, engineers rely on experiences and use 3D CAD software to design it by trial and error, however, the approach is inefficient and impossible to provide the optimal solution. In this paper, we propose a genetic algorithm and sequential quadratic programming based methodology to solve the problem and develop a software for engineers to complete the dimensional design of a spatial pointing mechanism. Experimental results validate the effectiveness and efficiency of the proposed approach, and engineers use the developed software to design a spatial pointing robot conveniently and accurately.