Abstract: Objective In order to prevent the gaps in coordinate datum between different regional continuously op-erating reference systems(CORS),we analyze the causes and introduce a method for coordinate da-tum unification.Using experimental data from the Hubei and Hunan CORS,the results show that thesystematic deviation reaches 17.9±4.5mm between these two datums.The proposed method establi-shes a unified coordinate datum to eliminate the systematic deviation and builds connections betweeneach coordinate datum.The validity of our method was supported by empirical evidence.Finally,some suggestions about coordinate datum unification for a regional CORS network combination are putforward.