This study was intended to evaluate the effects of catalysts on selectivity production of biomass microwave-assisted pyrolysis. Microcrystalline cellulose was investigated to the effect of pyrol- ysis temperature and microwave absorber （catalyst） on distribution and composition of products. The pyrolysis behavior of several major products was analyzed to conclude the evolution mechanism of cel- lulose. The results showed that furfurals and sugars were main component of pyrolysis products. It was proposed that the merit “internal heating” of microwave maybe promote three main sets of chemical pathways to describe the possible fission of cellulose, one ascribed to ring-opening of 3, 6-anhydro-glu- copyranose, two to second dehydration reaction of levoglucose, another to the formation of glucofuranose through structure rearrangement on C2 and C5. At the end of the study, an integrated model of cellulose pyrolysis was developed to improve the bio-oil quality.