The medical insurance gap refers to the fund gap when the medical insurance fund pays medical expenses, that is, the difference between the actual expenditure of the medical insurance fund and the payable expenditure. The medical insurance gap is caused by many reasons, such as rising medical expenses and aging population. The emergence of medical insurance gap will lead to insufficient payment ability of medical insurance fund and unable to meet people's medical needs. To ensure the sustainability of medical insurance fund, we must control the rise of medical expenses.