A method of optimizing planar transformers' design based on integrated software platform iSIGHT is presented.Through integrating the circuit simulation tool Saber and Maxwell 3D to the optimization tool iSIGHT,the parasitic effects on planar transformers are studied carefully.Changing the thickness of the insulator layer between the primary and the secondary can obtain different values of parasitic parameters and a new method to avoid parasitic oscillations with dangerous high voltage spikes to improve the SMPS performance is established.Hence an optimal design of planar transformer is obtained.The final optimal simulation analysis results verify the correctness of above theoretical study.