This paper proposes the design and implement-tation of simulator on a naval combat system. The proposed simulator has the functionality of data logging, logged data analysis, the BCU(Ballistic Computing Unit) S/W-modification based on the results of the logged data analysis, and performance evaluation of the artillery results whether that meet the requirements specification or not. The artillery performance can be evaluated by the simulation function of OSD(Own Ship Data) and target data or by the real data of OSD and target data. When the simulated artillery result satisfies the performance specifications, the BCU S/W is installed at the onboard system. The simulation results show that simulated artillery results are similar to the actual results.