The frequency and intensity of small medium earthquakes in the Luoerling—Zhufoan area,west of Huoshan county,are particularly prominent in Anhui province and its neighboring areas.The earthquakes in this area are characterized as moderately strong and concentrating into a band,with small ones clustering at shallow focal depth and forming a swarm.Based on the above,it is of critical and urgent importance to strengthen earthquake monitoring and improve location accuracy in the region.The double-difference (DD) location algorithm,as a relative positioning method,has unique advantages in improving the accuracy of earthquake location.From January 1,2009 to June 13,2014,2 679 earthquakes of M_L≥ 0.0 occurred in the Huoshan area,Anhui province,and we relocated them in this study using the DD method.The average relative errors in the focal depths were 0.05,0.06,and 0.07 km in the E-W,N-S,and U-D directions,respectively,as compared with the original values after relocation.The positioning accuracy of the original source location was greatly increased and the "grid" illusion distribution phenomenon of the original source location,caused by positioning errors,was significantly improved after relocation.The spatial distribution of the epicenters is more compact and concentrated than previously determined.The relocation results show that there are three dense seismic zones distributed along the NE direction,consistent with the direction of the Luoerling—Tudiling fault.The distribution of the focal depths is more precise and there is a predominant depth range from 4 to 9 km that accounts for over 88% of the total.More shallow earthquakes in the Huoshan area indicate that the upper crust may be in a period of higher seismic wave velocity.