A simplified turbulence model for predicating the in-cylinder turbulence parameters during combustion in a spark-ignition engine is investigated in this study. It is based on the standard k - ε model with the assumptions that no influence of squish and swirl is considered and that turbulence is in equilibrium. Hence it has a simplified form that meets the requirements for a two-zone quasi-dimensional combustion model.The proposed sub-model is implemented in a quasi-dimensional entrainment combustion model for spark-ignition engines. With this combustion model as the core system, a complete thermodynamics simulation system for a turbo-charged spark-ignition engine is programmed to simulate the working process and engine performance characteristics. After calibration against experimental date taken from a 4-cylinder turbocharged spark-ignition engine, some adjustable constants for the proposed turbulence model are fixed, and successful validation is thus made under variable engine operating conditions. The results show that the proposed turbulence model could present correct predication results for the turbulence parameters during combustion, and hence make this thermodynamics model more reasonable in calculating engine performance and working process.Finally, parametric studies are performed to analyze the sensitivity of the adjustable constants used in the proposed model to provide guidance for future study.