The invention discloses a process and a plant for preparing adipic acid by catalytically aerobically oxidizing cyclohexane. The process comprises the following steps: dissolving 1 to 50 PPM of a catalyst including single metalloporphyrin or mu-oxo bimetallic porphyrin or a mixture of single metalloporphyrin, mu-oxo bimetallic porphyrin and transition metal salt or oxide in cyclohexane; introducing 5 to 12 atm of air or oxygen-rich or oxygen-poor air into a multi-stage oxidation reactor with a gas distributor; controlling the reaction temperature at 140 to 160 DEG C; oxidizing cyclohexane for 45 to 120 min; feeding the mixture of the oxidation reaction into a flash separator to carry out flash evaporation at the temperature of 78 to 155 DEG C and under the pressure of 0.1 to 1.0 atm, so that the low-boiling-point products such as cyclohexane, cyclohexanol and cyclohexanone change to gas and are separated from adipic acid with the content above 80%; continuously circularly oxidizing the low-boiling-point products to separate and purify the high-boiling-point oxidation product; and purifying and separating by the existing technique to obtain fine adipic acid product. The process can directly prepare adipic acid by aerobically oxidizing cyclohexane, wherein the conversion rate of cyclohexane is up to 95%, and the yield of adipic acid is up to 70%.