To calculate aircraft performance data rapidly and accurately in conceptual design, a rapid method with performance analysis code based on MATLAB/ SIMULINK simulation is presented. The method is to read out the existed aero data, mass data, propulsion data and profile data from a database, and then differential equations of motion for each flight segment are constructed and solved respectively in SIMULINK. Finally, the results are saved to the original database. The whole solving process as well as pre-post process is controlled by MATLAB script.The performance analysis of a Boeing 737-800 civil jet is illustrated to validate the method. Compared to the engineering method, this method is more accurate and straight forward without much code, and easy to implement andmaintain. The method is quite appropriate for rapid implementation of performance analysis in civil jet conceptual design.