The invention relates to a magnetic developer, in particular to a toner used for a laser printer, which comprises components such as an adhesive resin, a magnetic material, a charge controlling agent, an internal additive and an external additive, wherein the main component adhesive resin adopts a styrene-butyl acrylate-butyl maleate terpolymer with the polymerization rate of 60:30:10, the melt index MI of 1.6 to 2.6 and the varnish viscosity of 140 to 380 CP; and the magnetic material adopts iron oxide or ferrite, and has the average particle size of 0.1 to 5 mu m, the coercive force of 20 to 1500 e, the saturation magnetization of 50 to 200 emv/g and the bulk density of 1.0 to 1.6 g/cm<3>. Novel schemes for material selection and proportioning are provided by the invention, and iron phthalocyanine is added. The toner produced by the invention ensures high image concentration, high resolution, high image definition, high fineness and non-adhesion of lines, non-adhesion to a fuser film and less abrasion to a photosensitive drum when used for the high-speed laser printer, and is particularly applied to the filling of a reusable cartridge of the high-speed laser printer.