The study investigates the co-integration between (the S&P 500 index)and (Dow Jones index) the DJIA by busing the method Engle-granger co-integration Test. The study use annual data from 1990 to 2016.The study examines the stability of the index of S&P 500 and DJIA using the E-views program through a unit root test. The study found that the indicators are unstable, but they become stable when taking the first difference. This condition integrates (the S&P 500 index) and (the DJIA index) during the long-term co-integration test. The analysis shows that there is a negative co-integration between the two variables. It should be emphasized that the short-term dynamic analysis showed a positive co-integration between both indexes. The study concluded that there is an urgent need to take into account the long-term negative co-integration between (the S&P 500 index) and (the DJIA index) by investors in the New York market. Also, the study considers short-term positive integration between (the S&P 500 index) and (DJIA index), which turns into a negative relationship in the long term when taking into account the markets linked with the New York market as a major global market and other international financial markets when making any financial investment. The result of this study could help users of major international financial markets in investment diversification to reduce risk.