The invention provides an alignment device for coupler installation. The alignment device comprises a support element, a probe, and an elastic element. A guiding hole is formed in the support element; and the probe is arranged in the guiding hole and can move along the guiding hole. The bottom surface of the support element is perpendicular to the moving direction of the probe. The bottom end of the probe is a contact terminal; and the contact terminal and the bottom surface of the support element are arranged on a same first plane. The two ends of the probe are exposed out of the two ends of the guiding hole. The probe is provided with a first scale segment; the first scale segment contains a first zero graduation line, a first positive scale zone, and a first negative scale zone, wherein the first positive scale zone and the negative scale zone are distributed at the two sides of the first zero graduation line; the first zero graduation line and the top end surface of the guiding hole are located at a same second plane, wherein the second plane and the first plane are parallel to each other. The elastic element s arranged in the guiding hole and is connected with the probe at a moving direction of the probe to exert resilience on the probe. According to the scheme, a conflict that the size of the device is gradually reduced and the large installation operation space is needed for field installation of a dial indicator can be eliminated.