Abstract: To improve the security of USB memory stick, this paper designs a U-disk locking system using the Android software certification based on a mobile phone. This paper introduces the security breaches existing in the process of using U-disk, discusses the composition and the working process of the system , and analyzes the system implementation. This paper develops a mobile control software (AC) and a control program of the locked U-disk (UK), gives flowcharts of AC and UK. Finally, by using an Android-based mobile phone as a unlock controller and using another Android-based mobile phone as a simulator of the locked U-disk, the system function is tested. The test results show that the design of the system achieves the desired objective with the good security. simplicity and practicability, laying a good foundation for the practical use of the U-disk locking system.