With unbalanced Chinese-English bilinguals as the subjects and the experiment of overt picture naming, this research aims to find out the answer to the question whether there is switch cost in the case of switch between languages belonging to different language families and to define the switch cost pattern in that case if the answer to the above question is affirmative. Results show that the length of preparation time has influence on the symmetry of switch cost. The analysis of ERP （Event Related Potentials） data shows that N2 effect exists both in language switch responses and language repeat responses.
