Abstract: The existing cost estimation models within the Earned Value Management (EVM) framework can not be well applied to mega construction projects (MCPs) with fixed duration.Firstly, the estimated total time (T₂) for all authorized work was estimated using earned schedule-based method, and the compressed duration was calculated by ΔT=T₂-T₀ at time t₀.Secondly,the Convex-exponential Time-cost function was used to estimate duration compressed cost (DCC), and the Gompertz Growth Model (GGM) was used to estimate the uncompressed EAC. On this basis, the estimation model for estimate at completion (EAC) of MCPs with fixed duration was proposed.Finally, taking the subproject of an airport project as a case, four basic estimation methods of traditional EVM and the improved estimation method were used to estimate its EAC respectively, and development trend of estimated deviations and their reasons for EACs of each model was systematically analyzed. The comparison results showed that the improved estimation method is more suitable for MCPs with fixed duration. The cost estimation model of this study improves the forecasting ability of traditional methods to estimate EAC within EVM framework, which is of practical significance to guide the MCPs with tight schedule in China.

Key words: fixed duration, mega construction project, estimate at completion, duration-compressed cost, EVM