Abstract: As the most basic source parameters, locations and local magnitudes of micro-earthquakes are of importance to the analysis and interpretation of micro-seismic data so that their accuracies are crucial. This study introduces a source location method called the virtual field optimization method (VFOM) and provides a parameter regression method which minimizes the station variance for an optimal local magnitude formula. The occurrence sources of a data set consisting of 401 events from the Yongshaba deposit of Kaiyang Mine are located using the VFOM, and an optimal local magnitude formula is regressed using the suggested method in this study. The results show that the locations are reliable and the station variances are significantly reduced. In addition, the bimodal characteristic is observed from the magnitude distribution obtained by the derived formula, indicating two different causes of the micro-seismic data. This study also demonstrates that the local magnitude formula should be regressed using the measured data for a new area, otherwise the magnitude distribution may lose some important characteristics.