This paper points out the limitations of the existing Markov model of DCF protocol based on un-fixed slot in ad hoc networks, and analyzes the difficulty of the modeling of DCF protocol in multi-hop ad hoc networks in detail. On the basis of this, this paper proposes a Markov model of DCF protocol based on fixed slot in multi-hop ad hoc networks. By solving this model, the theoretic value which reflects the saturated throughput performance of multi-hop ad hoc networks is obtained. The effectiveness of this model is demonstrated by the simulations in GloMoSim environment.