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A multi-zone model was used to predict the operating range of homogeneous charge compression ignition (HCCI) engine, the boundaries of the operating range were determined by knock (presented by ringing intensity), partial burn (presented by combustion efficiency) and cycle-to-cycle variations (presented by the sensitivity of indicated mean effective pressure to the initial temperature). A HCCI engine fueled with iso-octane was simulated, and it was found that the knock and cycle-to-cycle variations predicted by this model showed a satisfactory agreement with measurements under different initial temperatures and equivalence ratios, and the operating range was well reproduced by the model. Furthermore, the model was applied to develop the operating range for different engine speeds by changing initial temperature and equivalence ratio. Finally, the potential to expand the operating range of HCCI engines through two strategies, i.e. variable compression ratio and boost, were investigated.