Ramp metering is the most effective and direct method to control a vehicle entering a freeway. This study proposes a novel density-based ramp metering method. Existing methods typically use flow data that has low reliability, and they suffer from various problems. Furthermore, when ramp metering is performed based on freeway congestion, additional congestion and over-capacity can occur in the ramp. To solve these problems faced with existing methods, the proposed method uses the density and acceleration data of vehicles on the freeway and considers the ramp status. The experimental environment was simulated using PTV Corporation's VISSIM simulator. The Traffic Information and Condition Analysis System was developed to control the VISSIM simulator. The experiment was conducted between 2:00 PM and 7:00 PM on October 5, 2014, during severe traffic congestion. The simulation results showed that total travel time was reduced by 10% compared to existing metering system during the peak time. Thus, we solved the problem of ramp congestion and over-capacity.