Ab initio (MP2) and density functional theory (DFT) methods have been used to examine eight isomers of the singlet BeN4 species with the 6-311+G* basis sets. The most stable isomer is the D-2h planar structure. Several decomposition and isomerization pathways for the BeN4 species have been investigated. The D-2h planar, the C-2upsilon branched, the C-s linear, and the C-4nu pyramidal structures are all likely to be stable and to be observed experimentally due to their significant isomerizaion or dissociation barriers (20.9-125.3 kcal/mol). But the C-2nu bent, the C-2nu five-membered ring, and the C-2nu cage structures are kinetically unstable. Among the known BeN4 isomers, the C-s linear and the C-4nu pyramidal structures are suitable to be potential high-energy-density materials (HEDMs) due to their high dissociation energies and significant dissociation or isomerization barriers.