Solid-state anaerobic digestion (SS-AD) is a promising process for organic waste treatment. The feeding amount and packing density is an important factor to affect the mass transfer and operating efficiency in SS-AD. This study investigated three different loading amounts of substrates, with the packing densities as 269 g/L, 337 g/L and 422 g/L, which were labelled as Batch 1, Batch 2 and Batch 3, respectively. The agricultural wastes, chicken manure and corn straw, were applied as feeding substrates. Leachate recirculation was employed to enhance the mass transfer. Several operating parameters were tested and the spatial distribution of microbial communities as well as the kinetics of biogas production were analyzed. Batch 2 and Batch 3 both showed good performance, although the higher packing density and leachate recirculation caused blockage in Batch 3. In contrast, Batch 1 with inadequate load worked inefficiently. In Batch 2, the spatial distribution of microorganisms was relatively uniform. Petrimonas and Ruminofilibacter were the dominant bacteria. The genus of Methanosarcina held 81%-94% of the archaea. The recirculation of leachate not only promoted the distribution and degradation of organic matters, but also made the soluble substrates and intermediates aggregate in the lower layer, affecting the distribution of the microorganisms.