M-type BaFe12O19 nanocrystalline aggregations were prepared by the citrate sol-gel method, using Fe(NO3)3 and Ba(NO3)2 as raw materials, urea and ethanol as the soft template. The samples were investigated by SEM, TEM, FT-IR, XRD and VSM. SEM and TEM micrographs show the product is hollow nanocrystalline aggregations with microporous. XRD patterns indicate M-type BaFe12O19 aggregations with mesoporous are purity and well crystallinity, the average size of the primary crystals of the aggregations is 48nm. Saturation magnetization and coercivity of the aggregations is 55.3emu/g and 5403Oe, respectively, which are higher than these of previous BaFe12O19 nano-particles reported in the literature.