Abstract: A series of catalysts composed of Mo-Bi-Co-Fe-Ce-Cs-K were prepared by orthogonally varying the three key factors, the concentration of ammonium paramolybdate solution, pH value and calcination temperature. The physico-chemical properties of the catalysts were characterized by BET, TG-DSC and XRD. The catalytic performance for selective oxidation of isobutylene to methacrolein was studied by using a continuous fixed bed micro-reactor under atmospheric pressure. The results indicated that the activity of the catalysts increased with surface area increasing, and the selectivity decreased with pore diameter decreasing. The optimum preparation conditions of the catalysts were that the concentration of ammonium paramolybdate solution was 10%, pH ranged from 2 to 3 and calcination temperature was 500 ℃. For the catalyst prepared at the optimal preparation conditions, the experimental results showed that isobutylene conversion was 87.2%, selectivity to methacrolein was 72.0% and the yield of methacrolein was 62.7% at the experimental conditions of isobutylene∶air=6∶94, GHSV=3 600 h－1 and reaction temperature=360 ℃.