The invention discloses a high-strength kraft linerboard bleaching method, characterized in that alkaline thiourea dioxide aqueous solution prepared from sodium hydroxide and thiourea dioxide is adopted to bleach kraft linerboard pulp, the pulp is pretreated by using ethylene diamine tetraacetic acid and a viscosity protection agent before bleaching, the PH value of bleaching liquor is 10 to 11, bleaching time is 30 minutes, the temperature about 60 DEG C is kept, the pulp is bleached by selectively breaking chromophoric groups in the paper pulp through the reducibility of the thiourea dioxide, lignin in the pulp is not removed, the beneficial component in the pulp is protected while the bleaching effect is good, pollution and toxicity are avoided in the bleaching process, and human health is facilitated.