The invention discloses a test method and a test device for asphalt pavement crack load response relative displacement. The test method comprises steps as follows: a, a reference part and a sensor positioning part are arranged on two sides of a to-be-tested crack, and a horizontal linear displacement sensor and a vertical linear displacement sensor are fixedly arranged on the sensor positioning part; b, a test vehicle is stopped in positions of the reference part and the sensor positioning part in Step a; c, the sensors are started, the test vehicle slowly runs forwards and passes by the sensor positioning part and the reference part sequentially, after the test vehicle runs for a proper distance, the sensors are turned off, and the test is finished. The test device comprises the reference part, the sensor positioning part, the horizontal linear displacement sensor, the vertical linear displacement sensor and a controller. Compared with the prior art, the test method and the test device have the advantages that horizontal and vertical relative displacement between two plates of the crack can be measured accurately, and the cause and the development degree of the crack are determined through displacement features.