The magnetocaloric (MC) effect-based solid-state magnetic refrigeration (MR) technology has been recognized as an alternative novel method to the presently commercialized gas compression technology. Searching for suitable candidates with promising MC performances is one of the most urgent tasks. Herein, combined experimental and theoretical investigations on the magnetic properties, magnetic phase transition, and cryogenic MC performances of GdFe2Si2 have been performed. An unstable antiferromagnetic (AFM) interaction in the ground state has been confirmed in GdFe2Si2. Moreover, a huge reversible cryogenic MC effect and promising MC performances in GdFe2Si2 have been observed. The maximum isothermal magnetic entropy change, temperature-averaged entropy change with 2 K lift, and refrigerant capacity for GdFe2Si2 were 30.01 J kg−1 K−1, 29.37 J kg−1 K−1, and 328.45 J kg−1 at around 8.6 K with the magnetic change of 0–7 T, respectively. Evidently, the values of these MC parameters for the present AFM compound GdFe2Si2 are superior to those of most recently reported rare-earth-based MC materials, suggesting the potential application for active cryogenic MR.