Although highly active antiretroviral therapy (HAART) provides a powerful strategy for HIV treatment, it has been shown that HAART cannot eradicate all viruses in patients because of the existence of long-term reservoir. With the use of HAART, resistant strains develop and become the dominant species. Because the number of independent treatment regimens is limited, once resistance to all available drug classes arises, the patient will die. In this paper, we propose a drug switching strategy to minimize resistance risk of resistance and preserve long-term control of the HIV infection based on a simple model of HIV infection with persistent viral reservoirs.