Abstract: In this paper, the seismic relative location method Sbox method is used to relocate the earthquakes occurred from March 18, 2018 to May 21, 2020 in northwest Yunnan province based on the seismic phase reports from eryuan sub-instability station array and some Yunnan fixed stations. On this basis, the Yangbi M_S6.4 earthquake sequence in Yunnan province is analyzed. The results show that the Sbox method can significantly sharpen the seismic distribution image, increase the seismic clustering, and improve the resolution of seismic distribution to the deep structure. Yangbi M_S6.4 seismic sequence distribution and background seismic distribution have clear spatial compensating phenomenon. The rupture direction of the earthquake is from NW to SE. During a period of several years or longer before the Yangbi earthquake, small earthquakes developed at the northwest end and bottom of the rupture surface, forming a pre-rupture belt, however, in the seismic fault plane area of the Yangbi earthquake, relatively quiet area was formed before the earthquake until the Yangbi earthquake sequence filled the area.