CrO3 did a favorable performance in catalyzing oxidation reaction of 3-carene and oxygen. CrO3-Al2O3 with a loading rate of 39.21% was prepared from CrO3 and neutral Al2O3 by impregnation, which not only performed as well as CrO3, but also benefited in reducing the residual quantity of Cr in the reaction solution. Allylic oxidization dominated the reaction and hardly any epoxidation was happened, so three different α,β-unsaturated ketones were produced as main products, that were car-3-ene-2-one, car-2-ene-4-one and car-3-ene-5-one respectively. Many reaction factors were investigated for their effects on the reaction, including catalyst amount, temperature, time and oxygen flux. After a series of condition experiments, the optimum oxidation process was established as that catalyst amount was 3% of the mass of 3-carene, temperature was 25℃, time was 10h and oxygen flux was 25mL/min. By the optimum process a result was obtained with a conversion of 58.72% for raw material and a selectivity of 86.07% for the total α,β-unsaturated ketones, while 19.83% for car-3-ene-2-one, 4.61% for car-2-ene-4-one and 61.63% for car-3-ene-5-one respectively. During the separation of the oxidation product by vacuum rectification, car-3-ene-5-one was found to be very easily isomerized and converted, as which preparation and separation of 3,6,6-trimethylcyclohepta-2,4-dienone could be accomplished in one step. However, similar isomerization reactions were not happened for car-3-ene-2-one and car-2-ene-4-one in this process. Results showed that reduced pressure was a necessary condition for isomerization, and the lower the pressure, the easier the reaction would occur, and the higher the effect would be. A conversion of 99.62% for car-3-ene-5-one and a selectivity of 98.15% for 3,6,6-trimethylcyclohepta-2,4-dienone could be obtained while the pressure was 0.5kPa, temperature was 120℃ and time was 4h, which indicated that a pressure of 0.5 kPa completely satisfied the reaction requirement.