The invention discloses a method for preparing p-phenylene terephalamide pulp from short cut p-phenylene terephalamide waste fibers through pre-treatment and combined beating. The method comprises: pretreating the short cut p-phenylene terephalamide waste fibers with a 2 to 50 percent swelling agent at 20 to 60 DEG C for 1 to 24 hours first, wherein the bath ratio is (5-50):1; and then subjectingthe pretreated short cut p-phenylene terephalamide waste fibers to body fluid exhaustion and washing, preparing a suspension of fibers with a pulp mass concentration of 0.25 to 3 percent with the short cut p-phenylene terephalamide waste fibers, and beating by a two-stage combined bearing process of a trough-style pulp beater to obtain the p-phenylene terephalamide pulp. The method is characterized by taking the short cut p-phenylene terephalamide waste fibers as a raw material, using the swelling agent to pretreat the short cut p-phenylene terephalamide waste fibers, preparing the p-phenylene terephalamide pulp by the two-stage beating process, shortening time for beating, improving the added value of p-phenylene terephalamide waste fibers and preparing the p-phenylene terephalamide pulpwith excellent performance.