A machine room ventilation energy-saving device using phase-change materials relates to machine room ventilation equipment and aims to solve the problems of large power consumption of air conditioners in the prior machine room. The device comprises a shell, an air outlet motor set, an air inlet motor set, an air inlet door, a system controller, an air outlet shutter, a phase-change material package tube and a phase-change material body. The phase-change material body is packaged inside the phase-change material package tube. The phase-change material package tube is horizontally arranged inside the shell. The air outlet motor set and the air inlet motor set are respectively embedded at the bottom of the top surface and the rear surface of the shell. The air inlet door is arranged on the rear surface of the shell relative to the air inlet motor set in a way of sliding in the vertically direction. The system controller is embedded on the lateral side of the shell. One temperature sensorof the system controller is arranged outdoor, and the other one is arranged on the phase-change material package tube. Two control ends of the system controller are respectively connected with switches of the air outlet motor set, the air inlet motor set and the air inlet door. The air outlet shutter is arranged on the front surface of the shell. The device can utilize cold energy of a natural cold source to reduce indoor temperature, thereby reducing the use of air conditioners and reducing power consumption.