The shift quality is one of the most important factors that affect the vehicle performances of comfort, ride and drivability for vehicles equipped with dual clutch transmission (DCT). Assessing the shift quality first and then optimizing shift control strategy and algorithm by the guidance of assessment results to improve the vehicle performance is a useful idea for the development of DCT and other types of automatic transmissions. This paper defines the shift quality assessment criteria in detail for DCT from the control point of view. A shift quality assessment system and a DCT vehicle model used for validation of assessment system are built with MATLAB/Simulink tools. Through the co-simulation of DCT vehicle model and assessment system, the shift quality control objectives, namely the expected control range of each assessment criterion, are determined, which provide reference and guidance for the optimization of DCT shift control. The highest level of shift quality assessment is selected as the objective optimization function and the multi-objective genetic algorithm (MGA) is used to optimize the control strategy of clutch switch timing during the torque phase and inertia phase. The assessment results before and after the optimizations are observed through the simulation. The simulation results verify the correctness and effectiveness of the shift control strategy after optimization, and thereby the shift quality of DCT proves improved.