A process for catalytic cracking of hydrocarbon oils includes the step of contacting a hydrocarbon oil feedstock with a catalytic cracking catalyst in a reactor comprising a dilute-phase transport fluidized bed and a fast fluidized bed connected in series for reaction. In the fast fluidized bed, the axial solid fraction ε of the catalyst is controlled within the range of about 0.1 to about 0.2. When used for catalytic cracking of hydrocarbon oil feedstocks, particularly heavy feedstock oils, the process and system show lower yields of dry gas and coke, and good product distribution.