The LLC-type dual active bridge (DAB) converter as an isolated DC-DC converter attracts increasing attention nowadays because of the popularity of the renewable energy generation. However, in practical application, the DAB converter is often cascaded with other subsystems, which may lead to instability in the cascaded system due to impedance interactions. The voltage conversion gain (VCG) of the converter and stability of the cascaded system are two important performance indicators. To achieve both targets, this paper proposes a design approach to maintain both constant VCG and system stability at the same time. A design example is provided and experimentally verified.