The presentation I gave in my investment class about paris trading. I implemented a experiment using R language to identify good pairs from S&P 100 universe. The algorithm is to perform ADF test on the spread of two random stocks and find out the pairs with stationary spread (co-integrated pairs). Pairs identification period is from 2010/11 to 2012/10, test period is from 2012/11 to 2013/12. Finally I got 33 pairs out of 4950 candidates, and I conduct a summary on the experiment result.