This study aimed to identify the effect of internal control according to committee of sponsoring organization to reduce illegal financial transactions, specially money laundering transactions in commercial banks listen in Amman Stock Exchange. The researchers adopted an analytical descriptive approach. A specially – designed questionnaire was given to a (13) commercial bank. This questionnaire was given especially to (financial manager, internal auditing manager, internal auditing), each bank took only (3) questionnaire collected back (33) questionnaire from bank. Which is a named (85%), the researcher used analytical program which is spss to analyze this data. The study came up with the existence of a positive effect of the independent variable of the study (combined and separated) to reduce money laundering in commercial bank , the most effective was information and communication and low effective was performance monitoring , according to sample population. This study recommended using committee of sponsoring organization (COSO) in most of commercial bank, especially in control environment and improving it as they can. Key Words: Internal Control System, Organization, Stock Exchange, Amman.