The invention discloses a device for testing internal temperature fields of DPF (diesel particulate filter) carriers. The device comprises an industrial personal computer, a thermocouple mounting tool A, K type thermocouples, a thermocouple mounting tool B and a thermocouple automatic test system. The industrial personal computer is connected with the thermocouple automatic test system by serial communication bus, and the thermocouple automatic test system is connected with the K type thermocouples by a signal wire; the K type thermocouples are mounted on the thermocouple mounting tool A and the thermocouple mounting tool B and are compressed by compression nuts; the K type thermocouples are inserted in channels of the DPF carriers according to measuring point positional distribution. The temperatures of measuring points can be tested. A method for testing the internal temperature fields of the DPF carriers includes processes for partitioning DPF carrier grids, processes for computing the temperatures of grid nodes and processes for designing the internal measuring points of the DPF carriers. The device and the method have the advantages that distribution of the internal temperature fields of the DPF carriers can be computed by the aid of test software and can be displayed, and the positions and numerical values of the maximum temperature gradient can be given; test data can be stored in the industrial personal computer after the data are completely analyzed and processed.