This research aims to find out how to prevent Money Laundering through Know Your Customer Principles at Bank Aceh Kcp Sutomo and to analyze what are the inhibiting factors in preventing money laundering at this bank so that Bank AcehKcp Sutomo is able to provide solutions for effective implementation of Know Your Customer Principles in prevent customer transactions that lead to and are indicated for money laundering so that the bank's reputation and integrity are maintained. The research method used is descriptive qualitative. Data collection was carried out by means of interviews, observation and documentation. The data used comes from primary data sourced from the field and secondary data sourced from the literature. This research was conducted on Jl.Sutomo No.Rt.02, Pandau Hilir, East Medan District, Medan City, North Sumatra. The results of this research show that Know Your Customer Principles is a fairly effective way to prevent money laundering at Bank Aceh Kcp Sutomo, which in its implementation includes several policies including organizing policies, customer identification, system reporting and manual reporting to the center and by providing Bank Aceh employees with training. -Customer recognition training because there are still obstacles faced in implementing it both from within the bank itself and from its customers as well as prevention by studying the reputation and integrity management of Bank Aceh Kcp Sutomo.