The invention relates to an experiment device and method for monitoring rest oil distribution in a rock core in a carbon dioxide displacement rock core process. The invention mainly aims at providing the experiment device capable of being used for obtaining microscopic rest oil space distribution state in the rock core in the liquid-stage or super-critical state carbon dioxide oil displacement process, and an obtaining method. The device is characterized by consisting of a first storage tank, a second storage tank, a first pressurizing pump, a second pressurizing pump, a heater, a first cooler, a rock core clamper with a sealing packer, a CT (computed tomography) scanner, a solid filter, a liquid filter, a second cooler, a first control valve, a second control valve, a first pressure meter, a second pressure meter, a first temperature indicator, a second temperature indictor and other connecting pipe fittings. By using the method and the device, the rock core CT scanning can be realized in the displacement process; through the division processing on the CT scanning image, the microscopic rest oil distribution state of the rock core in the rock core during different-state carbon dioxide displacement is monitored.