On condition that the intrinsic decoherence is taken into account, the dynamic evolution of entanglement of a two-qubit XXZ Heisenberg system under the influence of various factors is investigated. It is found that the intrinsic decoherence obviously suppresses the time evolution of the entanglement whether the initial state is maximally entangled or not. When the initial state is the entangled state |ψ(0)〉=c|01〉+d|10〉, the system entanglement is clearly influenced by the Dzyaloshinskii-Moriya (DM) interaction and the intrinsic decoherence, and it is independent of the anisotropy and the external magnetic field. If the initial state is the entangled state |ψ(0)〉=a|00〉+b|11〉, the system entanglement suffers from not only the intrinsic decoherence but also the external magnetic field, and has nothing to do with the DM interaction and anisotropy.