This purpose of this research is to study, design and construct a device alarm system for dangerous leakage current distribution transformer in public area the real-time monitoring and alarm system. Test is determined and modeled using linear regression and polynomial using leakage current analysis and level dangerous in microcontroller for the real-time monitoring and alarm system. The result found was that the device and system can measure leakage current in the range 1 – 200 mA. The leakage current level could be set from 30 – 200 mA. The device error is not more than 4% which is acceptable. It is found that the system can correctly detect and report leakage current levels. with satis factory result.