In-house code which simulates the performance of pre-burner in staged-combustion liquid-fueled rocket engine was developed and demonstrated. Chemical reaction of pre-burner was modeled based on analytic algorithm of CEA (Chemical Equilibrium with Applications) and gas dynamics model was incorporated with it. Comparison results between in-house code and CEA have shown small relative errors except at very high or very low O/F ratio. Also the performance curve obtained by in-house code revealed that the calculated values follow the overall trend of real engine (RD-8) performance quite well and at steady-state operation, the deviation became very small. ???