The great Haiyuan earthquake occurred at 20：06：09 on December 16, 1920 in the south of Ningxia Hui Autonomous Region. The magnitude of this earthquake is 8.5, listed as one of the three greatest earthquakes to ever occur in Chinese continent. This devastating earthquake killed about 230,000 people according to previous reports. Recent studies show that total casualties may have reached 270,000. The study of this earthquake using modern scientific and technological methods is the first in the history of earthquake research in China. Significant breakthroughs took place in the middle of last century. The earthquake surface rupture, with 200km in length and prominent left-lateral strike-slip displacement, was discovered. The first monograph on the Haiyuan earthquake was published. In the 1980s, innovative large-scale geological mapping technology for active faults was developed during studies on the Haiyuan earthquake surface ruptures, with the publication of the first large-scale map of the Haiyuan active fault. Quantitative studies were carried out on the fine structure and geometry of the fault zone, Holocene slip rate, co-seismic displacement, paleoearthquake and recurrence intervals and future earthquake risk assessment. The innovative studies also included rupture propagation along the strike-slip fault, evolution of pull-apart basins, determination of total displacement of the strike-slip fault, transition equilibrium between strike-slip displacement along its major strand and crustal shortening at the end of the strike-slip fault, and the mechanism of deformation on Liupan Mountain. On the occasion of the 90th anniversary of the Haiyuan earthquake, careful retrospect of scientific progress achieved during the recent 20 years would be helpful in providing further direction in the study of active faults and earthquake hazard reduction. While taking this occasion to remember those lost by the Haiyuan earthquake, we aim to make greater contributions to earthquake prediction and seismic hazard reduction.