Abstract: The carbonated deep mixing method is an innovative CO₂ consuming method for ground improvement, in which the MgO binder is firstly mixed with the soft soils and then CO₂ is injected for carbonating in few hours. Using the carbonated mixing method, higher soil-MgO stabilized strength can be obtained in very short time. The influence of MgO activity on the stabilization efficiency and its mechanism were studied in this paper. A typical clay from Wuhan was used as the target soil and three different activities of MgO were selected as binders for laboratory tests. The results show that the carbonated degree with different active MgO binders can be predominantly completed in 3~6 hours and reaches stability after 24 hours. There are almost the same volume expansion of about 16% during carbonating process at all MgO binders. While the MgO activity has significant influences on the efficiency of the carbonated mixing method. With the higher activity MgO binder, the higher carbonated degree and more carbonated products forming denser texture are observed. Its unconfined compressive strength after carbonating 6 hours with higher activity MgO gets to the similar strength of 28 day-cured cement-stabilized soils. The final strength with higher activity MgO carbonated mixing soils can reach 2.5 MPa, while that with much lower activity MgO is only 0.5 MPa. The carbonated MgO-stabilized soils have considerable lower pH value (9.0~9.6) than the pH value (12) of the cement-stabilized soils.