The problem of EMI reduction is the topic of major interest in recent years. EMI reduction is one of the aspects in the power converter operation and control. EMI Reduction refers to techniques such as spread spectrum clocking to reduce the effects of electromagnetic interference or EMI,EMI is defined as EMI = kIAf2 where I is the current, A is the loop area, f is the frequency, and k is the constant depending on PCB materials and other factors. Among various dc/dc converters, LLC resonant converter has been attracting more and more attention for its inherent merits, like soft switching, low EMI, high efficiency, and high power density. In this paper how EMI can be reduced by using LLC resonant converter and their modeling and designing methodologies presented.