The invention discloses an epoxy resin composition containing a vanillic aldehyde-based phosphorus containing flame retardant. The epoxy resin composition comprises epoxy resin, a curing agent, a curing accelerant, a primary flame retardant and a flame retardant additive and etc. The flame retardant additive is the vanillic aldehyde-based phosphorus containing flame retardant The invention also discloses an application of the epoxy resin composition, for example, an application of the epoxy resin composition or a cured product thereof as a flame retardant material. When the epoxy resin composition disclosed by the invention is cured and used as a flame retardant material, compared with an existing intumescent fire retardant epoxy system, the epoxy resin composition not only is more excellent in flame retardant property and mechanical property, but also has double functions of saving resources and protecting the environment as the flame retardant additive uses sustainable vanillic aldehyde as a raw material.