The purpose of this study is to analyze the performance of a spark ignition (SI)-HCNG (Hydrogen Compressed Natural Gas) engine by KIVA-3V. Turbulent premixed combustion is modeled by an independent transport equation for the mean reaction progress variable. The turbulent burning velocity is given by a phenomenological correlation in terms of laminar flame speed and turbulent intensity. The resulting flame speeds are validated against measured data in literature with parametric variation of turbulent intensity and H₂ fraction. Results showed good agreement with measured efficiencies and NOx emissions for varying air/fuel ratios and hydrogen fractions in CNG fuel. It is shown possible to satisfy the target of improved efficiency and reduced NOx of the test SI-HCNG engine due to enhanced lean flammability limits of CNG premixture with hydrogen.