The lateral force calibration is a key procedure for applications of atomic force microscopes. Among different calibration methods, the diamagnetic lateral force calibration (DLFC) method has been widely used due to its ease of use as well as being able to estimate the cross talk conversion factor and achieve very small stiffness. The lateral stiffness of the system is the only parameter in the DLFC method; however, its dependence on the properties and parameters of the DLFC system remains unexplored. In this paper, a theoretical formulation of such dependence is developed and experimentally verified. These results provide a guidance to design and optimize future DLFC systems with better applicability and precision in calibrations. As an example, we optimized a DLFC system such that it is robust against normal load, which is previously assumed impossible.