The purposes of the research were to find out the significances of the implementation of simulation technique and the using of posters as visual aids in improving students’ social interaction and creative thinking. Semester II English students of Muslim Nusantara University Medan were selected as the population of the research, then, two classes were chosen of the sample of the research y applying random purposive sampling. Moreover, quantitative research method was used with factorial design 2 X 2 to achieve the aims of the research. based on the data analyzed, this research found out that students’ social interaction taught by implementing simulation technique and using the poster was being extremely higher with 80,05 than experimental class II with 68,68. Then, the indicator average of creative thinking also showed a very significant effect in which experimental class II was 86,69, while experimental class II was only 60,75. Moreover, there was an interaction occured between technique simulation with the poster with student’s creative thinking toward students’ social interaction with Fobsesrved>Ftablewith 294,740 > 4,00 and Sig < 0,05 with 0,000< 0,05, and with Fobsesrved189,190 >Ftable4,00 and with Sig 0,000 < 0,05. Last, there was an interaction between simulation technique and poster in which simulation technique was being much more effective combined with poster as visual aids with sig <prob (0,000 < 0,05). In conclusion, students whose higher creative thinking in creating the poster would have higher social interaction in EFL speaking class in which the more frequent student’ social interaction in the classroom, the higher speaking skill achieved.