Abstract: The variations of geomagnetic field total intensity of Lunan mobile geomagnetic observation network before and after the Cangshan M 5.2 earthquake have been analyzed and studied. It is considered that the anomaly of the geomagnetic field total intensity of this region was the response of the Cangshan M 5.2 earthquake, the epicenter is right located near the anomalous zone of the geomagnetic field.