The loess tableland has complex surface conditions，and CO₂ flooding in ultra-low permeability reservoirs faces the high density of well patterns，the high injection pressure，and the easy gas channeling. Moreover，the development is characterized by water-alternating-gas injection to mitigate gas-channeling.As a result，there are multiple CO₂ leakage points and high intensity in this area，so the layout and monitoring accuracy of CO₂ monitoring points are demanding，and the existing safety monitoring systems are hardly applicable. In view of these problems，according to the identification of CO₂ leakage risks in ultra-low permeability reservoirs in the loess tableland and the analysis of CO₂ spatial migration in geological bodies，a three-dimensional multi-index CO₂ safety monitoring system was established，covering cap rock，wellbores，deep and shallow groundwater，soil，surface water，and atmosphere. Besides，CO₂ safety monitoring was practically carried out to further build a safety evaluation system of CO₂ storage. From the results of safety monitoring and evaluation，there was no abnormality for all indexes after CO₂ injection and no CO₂ geological leakage occured in the test area. The safety of CO₂ storage was at the levelⅠ.