The decomposition of plant residues plays an important role in the substance circulation, especial carbon-nitrogen cycle, which is influenced by many microorganism that acts the role of the consumer and decomposer could directly and indirectly accelerated the degradation process. As a member of microorganism, mycorrhizas are recognized as being of special importance as it has an especial microhabitat. Arbuscular mycorrhizal (AM) fungi form mutualistic symbiosis with more than 80% of the higher plant species. The contribution of AM to plant residues' degradation process varied at different hierarchical levels: plant root, mycorrhizas and the soil mycelium, of course the accompanying bacteria should be mentioned. In previous studies, most experiments were carried out with pot or other single compartment devices, this made it difficult to clarify different effects of mycorhiza symbiosis on plant residues degradation. In present study, the split-root device with four compartments was used to quantitatively compare the change of degradation process in rhizosphere, mycorrhizosphere and hyphaesphere. We choose maize straw as the representative of plant residue, AM fungus, Glomus mosseae (G. m) was inoculated. Harvested samples respectively in 20, 30, 40, 50 and 60 days, and then analysed the effects of soil enzymatic activity, soil microbial biomass carbon and nitrogen, soil respiration, discuss mechanism of mycorrhizal inoculation accelerate maize straw degradation. The results showed that inoculation with G. m, the maize straw degradation mass and degradation coefficient in mycorrhizal compartment were higher than that in root compartment at all stages, Mycorrhizal inoculation enhanced C release but prejudiced N release, and then reduced the C/N ratio, and so as to facilitate its further degradation. For the soil biological performance, we found that the catalase, protease, acid phosphatase, microbial biomass carbon and soil respiration have been enhanced in mycorrhizal compartment compared with root compartment, and the same as hyphae compartment with soil compartment, formed the active microbial community further. The increase of these indexes involved in the degradation process, and become the important reasons for mycorrhizal speed up the degradation. More AM fungal species and soil types will be considered in our following studies.