Abstract: Adding phosphorus to the epoxy resin system could effectively improve its liquid oxygen compatibility. Anyway, the research about mechanical properties of such epoxy resin system containing phosphorus was absent. Since the cured phosphorus-containing epoxy resin system had a complex and amorphous interlaced network structure, and there were many interrelated factors affecting its mechanical properties, it was difficult to demonstrate the microscopic fracture behavior by experiments. In the present paper, based on molecular dynamics (MD) research, the curing and cross-linking process of epoxy resin containing phosphorus (synthesized from 10-(2, 5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) and epichlorohydrin and 4, 4'-diaminodiphenylmethane (DDM) was simulated. The thermodynamic parameters and microscopic failure beha-vior of the resin system were calculated, and the micromechanical response mechanism under the fracture process was revealed. And the results were compared with another phosphorus containing epoxy resin system (ODOPB modified epoxy) with 2wt% phosphorus content. The analysis results provide a reference for the design and performance optimization of high-performance epoxy composites with extreme environment resistance.