Early diagnosis faults of power transformers which is an equipment part of the electric energy transmission and distribution system protects system and equipments. Power outages and financial loses are perevented thanks to diagnosis of transformers faults by ensuring continuity of efficient and high quality working conditions. Dissolved Gas Analysis (DGA) has ability to detect incipient faults of transformers. When any fault occur in power transformers, some gases dissolved in transformer oil. These gases are interpreted the DGA systems. When DGA is carried out i-) Conventional Methods and ii-) Intelligents Systems are used. The conventional systems have limitations. Intelligent systems overcome limitations. In this paper a Fuzzy Logic application is implemented to increase reliability of IEC Ratio, which is one of the DGA methods. The outputs have show that the intelligent system which we used is over the conventional method called IEC Ratio.